Digital SAT maths isn’t very difficult if you give it enough time and practise consistently. However, some questions can be really hard, and you need to scratch your head to get them right- something that is challenging when there’s a time crunch. To help you gain an understanding of what you’re up against, here are 15 of the hardest SAT questions with their solutions, that cover the domains of Algebra, Data Analysis, Geometry, and Trigonometry.
Domain Algebra
Domain algebra consists of problems of the types- Linear equations in 1 and 2 variables, Linear functions, Systems of 2 linear equations in 2 variables and Linear inequalities in 1 or 2 variables.
Questions from this domain are framed to confuse the student, and thus, it is important to learn how to navigate word-play during the test.
Let’s go through some examples:
Q1: (Dec’23 Digital SAT)
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The function f is defined by the given equation. For what value of k does f(k)=6k+3?
Solution:
1. Formulate the Equation:
|8 - 5k| = 6k + 3
2. Consider the absolute value:
The equation |8 - 5k| = 6k + 3 can be split into two cases because of the absolute value:
Case 1: 8 - 5k = 6k + 3
8 - 3 = 11k
5 = 11k
k = 5/11
8 - 5 * (5/11) = 8 - 25/11 = 63/11
6 * (5/11) + 3 = 30/11 + 33/11 = 63/11
So, k = 5/11 works for this case.
Case 2: 8 - 5k = -(6k + 3)
8 - 5k = -6k - 3
8 + 3 = -6k + 5k
11 = -k
k = -11
8 - 5 * (-11) = 8 + 55 = 63
6 * (-11) + 3 = -66 + 3 = -63
63≠-63, so k = does not work.
Thus, the values of k that satisfy f(k) = 6k + 3 are k = 5/11.
Q2: (Dec’ 23 Digital SAT)
For groups of 28 or more people, an arcade charges $9 per person for the first 28 people and $15 for each additional person. How many total people were in attendance if the group paid $447 to go to the arcade?
Solution:
Let's first calculate the total cost for the first 28 people and then determine how many additional people could attend based on the remaining amount:
Each of the first 28 people pays $9, so:
Cost for 28 people = 28 * $9 = $252
Total paid = $447
Remaining amount = $447 - $252 = $195
Each additional person costs $15.
Number of additional people = Remaining amount / Cost per additional person
Number of additional people = $195 / $15 = 13
Total people = First 28 people + Additional people
Total people = 28 + 13 = 41
Thus, there were 41 people in total in attendance at the arcade.
Q3: If 3x−y=12, what is the value of 8x/2y?
A) 212
B) 44
C) 82
D) The value cannot be determined from the information given.
Solution:
So that the numerator and denominator are expressed with the same base. Since 2 and 8 are both powers of 2, substituting 23 for 8 in the numerator of 8x/2y gives
(23)x/2y
Since the numerator and denominator/tor of have a common base, this expression can be rewritten as 2(3x−y). In the question, it states that 3x−y=12, so one can substitute 12 for the exponent, 3x−y, which means that
8x/2y=212
The final answer is A.
Q4: The incomplete table above summarises the number of left-handed students and right-handed students by gender for the eighth-grade students at Keisel Middle School. There are 5 times as many right-handed female students as there are left-handed female students, and there are 9 times as many right-handed male students as there are left-handed male students. If there are a total of 18 left-handed students and 122 right-handed students in the school, which of the following is closest to the probability that a right-handed student selected at random is female? (Note: Assume that none of the eighth-grade students are both right-handed and left-handed.)
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A) 0.410
B) 0.357
C) 0.333
D) 0.250
Solution:
Let x be the number of left-handed female students and let y be the number of left-handed male students.
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Using the information given in the problem, the number of right-handed female students will be 5x, and the number of right-handed male students will be 9y. Since the total number of left-handed students is 18 and the total number of right-handed students is 122, the system of equations below must be true:
x+y=18
5x+9y=122
Thus, 5*10, or 50, of the 122 right-handed students are female. Therefore, the probability that a right-handed student selected at random is female is 50122, which to the nearest thousandth is 0.410.
The final answer is A.
Domain Advanced Math
Domain Advanced Math needs you to have a high accuracy, speed, and understanding of logs, and graphs. It revolves around some of the most difficult concepts, and questions that require serious thinking are formed from it.
Let’s have a look at a few questions that will help you ascertain what to expect:
Q5: (8-i) / (3 - 2i)
If the expression above is rewritten in the form a+bi, where a and b are real numbers, what is the value of a? (Note: i=−1)
Solution:
To rewrite (8-i) / (3 - 2i) in the standard form a + bi, multiply both the numerator and denominator by the conjugate of the denominator, which is (3 + 2i).
[(8 - i) * (3 + 2i)] / [(3 - 2i) * (3 + 2i)]
(8)(3) + (8)(2i) - (i)(3) - (i)(2i)
= 24 + 16i - 3i - (-1)(2)
= 24 + 16i - 3i + 2
= 26 + 13i
(3)(3) - (2i)(2i)
= 9 - (-4)
= 9 + 4
= 13
(26 + 13i) / 13 = 26/13 + 13i/13 = 2 + i
Thus, when (8-i) / (3 - 2i) is rewritten in the standard form a + bi, the value of a is 2.
Q6: For a polynomial p(x), the value of p(3) is −2. Which of the following must be true about p(x)?
A) x−5 is a factor of p(x).
B) x−2 is a factor of p(x).
C) x+2 is a factor of p(x).
D) The remainder when p(x) is divided by x−3 is −2.
Solution:
If the polynomial p(x) is divided by a polynomial of the form x+k (which accounts for all of the possible answer choices in this question), the result can be written as
p(x)/x+k=q(x)+r/x+k
where q(x) is a polynomial and r is the remainder. Since x+k is a degree-1 polynomial (meaning it only includes x1 and no higher exponents), the remainder is a real number.
Therefore, p(x) can be rewritten as p(x)=(x + k)q(x) r, where r is a real number.
The question states that p(3)=−2, so it must be true that
−2=p(3)=(3+k)q(3)+r
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Now we can plug in all the possible answers. If the answer is A, B, or C, r will be 0, while if the answer is D, r will be −2.
A. −2=p(3)=(3+(−5))q(3)+0
−2=(3−5)q(3)
−2=(−2)q(3)
This could be true, but only if q(3)=1
B. −2=p(3)=(3+(−2))q(3)+0
−2=(3−2)q(3)
−2=(−1)q(3)
This could be true, but only if q(3)=2
C. −2=p(3)=(3+2)q(3)+0
−2=(5)q(3)
This could be true, but only if q(3)=−25
D. −2=p(3)=(3+(−3))q(3)+(−2)
−2=(3−3)q(3)+(−2)
−2=(0)q(3)+(−2)
This will always be true no matter what q(3) is.
Of the answer choices, the only one that must be true about p(x) is D, that the remainder when p(x) is divided by x−3 is -2.
Thus, the final answer is D.
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Q7: The function f(x)=x3−x2−x−11/4 is graphed in the xy-plane above. If k is a constant such that the equation f(x)=k has three real solutions, which of the following could be the value of k?
Solution:
The equation f(x)=k gives the solutions to the system of equations
y=f(x)=x3−x2−x−11/4
and
y=k
The graph of y=k is a horizontal line that contains the point (0,k) and intersects the graph of the cubic equation three times (since it has three real solutions).
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Given the graph, the only horizontal line that would intersect the cubic equation three times is the line with the equation y=−3, or f(x)=−3. Therefore, k is −3.
The final answer is D.
Q8: (March'24 Digital SAT)
f(x) = 5(0.92)³Ë£
The function f is defined by the given equation. The equation can be rewritten as f(x) = 5(1 - p/100)Ë£, where p is a constant. Which of the following is closest to the value of p?
A) 8
B) 12
C) 22
D) 24
Solution:
The function f(x) is defined as follows:
f(x) = 5(1 - p/100)x
And this function is equivalent to:
f(x) = 5(0.92)3x
To find the value of p, set the expressions inside the parentheses equal to each other:
1 - p/100 = 0.923
Calculate 0.92 raised to the power of 3:
0.923 is approximately 0.778688
Solve for p:
1 - 0.778688 = p/100
0.221312 = p/100
Multiply both sides by 100 to solve for p:
p = 0.221312 * 100
p = 22.1312
Since p needs to be an integer, round p to the nearest integer within the given choices:
p ≈ 22
Thus, the answer is p=22.
Q9: (Nov 23 Digital SAT)
y = 3x² - 5x - 12
40x - 4y = a
In the given system of equations, a is a positive constant. The system has exactly one distinct real solution. What is the value of a?
Solution:
40x - 4y = a
y = 10x - a/4
Replace y in y = 3x^2 - 5x - 12 with the expression from the linear equation:
10x - a/4 = 3x^2 - 5x - 12
Move all terms to one side:
3x^2 - 15x + a/4 - 12 = 0
The discriminant of a quadratic equation ax^2 + bx + c = 0 is given by:
Discriminant = b^2 - 4ac
Apply this to our equation:
a = 3, b = -15, c = a/4 - 12
Calculate the discriminant:
(-15)^2 - 4 3 (a/4 - 12) = 0
Solve for a:
225 - 3(a - 48) = 0
225 - 3a + 144 = 0
369 = 3a
Thus, the answer is that a = 123.
Domain Problem Solving and Data Analysis
This domain tests your reasoning skills and ability to statistically analyse mathematical data. More Arithmetically oriented, the domain problem solving and data analysis section tests percentages and ratios, and evidence-based decision making. The following examples illustrate the kind of questions you might expect.
Q10: A gear ratio r:s is the ratio of the number of teeth of two connected gears. The ratio of the number of revolutions per minute (rpm) of two gear wheels is s:r. In the diagram below, if Gear A is rotated by the motor at a rate of 100 rpm, what is the number of revolutions per minute for Gear C?
A) 50
B) 110
C) 200
D) 1,000
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Solution:
Because gears A and C do not connect directly, but instead through gear B, we should first try to figure out the rotational relationship between A and B (at 100 rpm) before applying that to B and C.
Because B is larger than A (and has more gears), A is going to rotate fully multiple times before B rotates once.
A has 20 gears.
B has 60 gears.
So A is going to have to rotate three times before B rotates once. (20 goes into 60 three times.)
Therefore, the ratio of rotation between A and B is 3 : 1.
B has 60 gears.
C has 10 gears.
Here, B only has to rotate a sixth of its distance for C to rotate once, so the ratio of rotation between B and C is 1 : 6.
So if Gear A rotates 100 times per minute, Gear B will rotate a third of that distance…
So we divide 100 by 3.
So we get (100)(â…“)(6).
Which gives us 200 rpm.
Thus, the final answer is C.
Q11: If x is the average (arithmetic mean) of m and 9, y is the average of 2m and 15, and z is the average of 3m and 18, what is the average of x, y, and z in terms of m?
A) m+6
B) m+7
C) 2m+14
D) 3m+21
Solution:
Since the average (arithmetic mean) of two numbers is equal to the sum of the two numbers divided by 2, the equations x=(m+9)/2, y=(2m+15)/2, z=(3m+18)/2 are true.
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The average of x, y, and z is given by (x+y+z)/3. Substituting the expressions in m for each variable (x, y, z) gives
[(m+9)/2 + (2m+15)/2 + (3m+18)/2] /3
The final answer is B.
Domain Geometry and Trigonometry
This section in SAT tests your knowledge of core geometric and trigonometric principles. The concepts here often connect to real-world applications and require you to be precise in your calculations. The following questions will help you get an idea of what to expect.
Q12: (March’24 Digital SAT)
3x2+18x+3y2−6y−15=0
The equation above gives the graph of a circle in the xy plane. If the circle is inscribed in a square, what is the area of the square?
Solution:
To solve the problem of finding the area of the square inscribed in the circle represented by the given equation, we first need to rewrite and simplify the circle's equation to find its centre and radius:
Start with the equation 3x² + 18x + 3y² - 6y - 15 = 0.
Divide every term by 3 to simplify:
x² + 6x + y² - 2y - 5 = 0.
For x:
x² + 6x -> Complete the square by adding and subtracting (6/2)² = 9.
(x + 3)² - 9.
For y:
y² - 2y -> Complete the square by adding and subtracting (-2/2)² = 1.
(y - 1)² - 1.
Substitute the completed squares back into the equation:
(x + 3)² - 9 + (y - 1)² - 1 - 5 = 0.
Combine and rearrange:
(x + 3)² + (y - 1)² = 15.
The circle is centred at (-3, 1) with a radius of √15).
The side of the square equals the diameter of the circle:
Side = 2 √(15).
Area = s² = (2 √(15))² = 60.
Thus, the area of the square inscribed in the circle is 60 square units.
Q13: Points A and B lie on a circle with radius 1, and arc AB has a length of π/3. What fraction of the circumference of the circle is the length of arc AB?
Solution:
To figure out the answer to this question, you'll first need to know the formula for finding the circumference of a circle.
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The circumference, C, of a circle is C=2πr, where r is the radius of the circle. For the given circle with a radius of 1, the circumference is C=2(π)(1), or C=2π.
To find what fraction of the circumference the length of AB⌢ is, divide the length of the arc by the circumference, which gives π/3 ÷ 2π. This division can be represented by=1/6.
The final answer is 1/6, 0.166, or 0.167.
Q14: A grain silo is built from two right circular cones and a right circular cylinder with internal measurements represented by the figure above. Of the following, which is closest to the volume of the grain silo, in cubic feet?
A) 261.8
B) 785.4
C) 916.3
D) 1047.2
Solution:
The volume of the grain silo can be found by adding the volumes of all the solids of which it is composed (a cylinder and two cones).
The silo is made up of a cylinder (with height 10 feet and base radius 5 feet) and two cones (each with height 5 ft and base radius 5 ft)![]()
These can be used to determine the total volume of the silo. Since the two cones have identical dimensions, the total volume, in cubic feet, of the silo is given by
which is approximately equal to 1,047.2 cubic feet.
The final answer is D.
Q15: (Digital SAT October 23)![]()
In geometry, a square pyramid is a pyramid that has a square base and four lateral faces. Square pyramid A is similar to Square pyramid B. The table gives the volumes, in cubic inches, of the two square pyramids. If the height of Square Pyramid A is 8 inches, what is the perimeter of the square base of Square Pyramid B, in inches? (Round your answer to the nearest tenth of an inch.)
Solution:
To solve this problem, we need to find the perimeter of the square base of Square Pyramid B, given the volumes of both pyramids and the height of Square Pyramid A. Here's how we can approach this using simple text math notation:
Volume of Square pyramid A = 16 cubic inches
Volume of Square pyramid B = 5488 cubic inches
Volume ratio = Volume of B / Volume of A = 5488 / 16 = 343
Volume ratio = k³ (where k is the scale factor between the pyramids)
343 = k³
k = cube root of 343
k = 7
Volume of a pyramid = (1/3) Base Area Height
Let s be the side length of the square base of Pyramid A.
Volume of A = (1/3) s² 8
16 = (1/3) s² 8
16 = (8/3) * s²
s²= (16 * 3) / 8
s²= 6
s = √((6)
s approximately equals 2.45 inches
Side length of B = 7 * Side length of A
Side length of B = 7 * 2.45
Side length of B approximately equals 17.15 inches
Perimeter = 4 * Side length
Perimeter = 4 * 17.15
Thus, the perimeter approximately equals 68.6 inches.