PSAT Math : Arithmetic

Study concepts, example questions & explanations for PSAT Math

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Example Questions

Example Question #1 : How To Find The Missing Number In A Set

Which number completes the following series: 1, 2, 4, 8, 16, 32, 64, _?

Possible Answers:

Not enough information

16

64

128

15

Correct answer:

128

Explanation:

All of the numbers in this series are 2n-1. The number that we are looking for is the eighth number. So 28–1 = 27 = 128.

Example Question #2 : How To Find The Missing Number In A Set

Alhough Danielle’s favorite flowers are tulips, she wants at least one each of three different kinds of flowers in her bouquet. Roses are twice as expensive as lilies and lilies are 25% of the price of tulips. If a rose costs $20 and Danielle only has $130, how many tulips can she buy?

Possible Answers:

4

3

2

5

1

Correct answer:

2

Explanation:

She can only buy 2 tulips at $80, because if she bought 3 she wouldn’t have enough to afford the other 2 kinds of flowers.  She has to spend at least 30 dollars (20 + 10) on 1 rose and 1 lily.

Example Question #1 : How To Find The Missing Number In A Set

Which of the following is not a rational number?

Possible Answers:

.001

√2

1.75

0.111...

5

Correct answer:

√2

Explanation:

A rational number is a number that can be written in the form of a/b, where a and b are integers, aka a real number that can be written as a simple fraction or ratio. 4 of the 5 answer choices can be written as fractions and are thus rational. 

5 = 5/1, 1.75 = 7/4, .001 = 1/1000, 0.111... = 1/9

√2 cannot be written as a fraction because it is irrational. The two most famous irrational numbers are √2 and pi. 

Example Question #1 : Sets

Which set represents all the single-digits integers (0-9) that are either prime, a perfect square, or found in the number 68?

Possible Answers:

\dpi{100} \small \left \{2,3,4,5,6,7,8,9 \right \}

\dpi{100} \small \left \{0,2,3,5,6,7,8 \right \}

\dpi{100} \small \left \{1,2,3,4,5,6,7,8,9 \right \}

\dpi{100} \small \left \{ 0,1,2,3,4,5,6,7,8,9 \right \}

\dpi{100} \small \left \{1,3,4,5,7,9 \right \}

Correct answer:

\dpi{100} \small \left \{ 0,1,2,3,4,5,6,7,8,9 \right \}

Explanation:

The prime digits are 2, 3, 5, and 7.

The perfect square digits are 0, 1, 4, and 9.

The only digits not represent in these two groups are 6 and 8, which are, coincidentally, found in the number 68.

Example Question #351 : Arithmetic

If four different integers are selected, one from each of the following sets, what is the greater sum that these four integers could have?

W = {4, 6, 9, 10}

X = {4, 5, 8, 10} 

Y = {3, 6, 7, 11}

Z = {5, 8, 10, 11}

Possible Answers:

39

41

40

38

42

Correct answer:

38

Explanation:

By observing each of these sets, we can easily determine the largest number in each; however, the problem is asking for us to find the greatest possible sum if we select four different integers, one from each set. The largest number is 11. We will either select this number from set Y or set Z.

We will select set

Y for the 11

because the next larger number in set

Z is 10, which is greater than the next largest number is set Y, 7.

We can use set Z for 10.

Because the 10 has already been selected, choosing the integer from W and X should be easy because 9 is the next largest integer from set W

and 

8 is the next largest integer from set X.

11 + 10 + 9 + 8 = 38

Example Question #1 : Counting / Sets

A team has a win-loss ratio of 4:1. If the team wins six games in a row, the win-loss ratio will now be 6:1. How many losses did the team have initially?

Possible Answers:

1

4

5

3

2

Correct answer:

3

Explanation:

If a team's ratio of wins to losses increases from 4:1 to 6:1 by winning six games, they must have 12 wins initially and 3 losses. 

Example Question #2 : Sets

Find the missing number in the following set:

Possible Answers:

Correct answer:

Explanation:

The rule is as follows: add 2 to the previous number then multiply times 2.

The answer is (16 + 2) * 2 = 36.

Example Question #2 : How To Find The Missing Number In A Set

 

If the average of Set  is , what is the average of Set ?

Possible Answers:

Correct answer:

Explanation:

We know the average of Set A is 5. Therefore:

Now let's solve for :

We can now plug this value of  into Set B and solve for the average:

Set B = {0, 2, 4}

The average of Set B is 2.

Example Question #1 : Consecutive Integers

The sum of three consecutive even integers is 108.  What is the largest number?

Possible Answers:

42

36

38

40

34

Correct answer:

38

Explanation:

Three consecutive even integers can be represented by x, x+2, x+4.  The sum is 3x+6, which is equal to 108.  Thus, 3x+6=108.  Solving for x yields x=34.  However, the question asks for the largest number, which is x+4 or 38.  Please make sure to answer what the question asks for!

You could have also plugged in the answer choices.  If you plugged in 38 as the largest number, then the previous even integer would be 36 and the next previous even integer 34.  The sum of 34, 36, and 38 yields 108.

Example Question #1 : Consecutive Integers

The sum of three consecutive even integers equals 72. What is the product of these integers? 

Possible Answers:

13728

12144

13800

17472

10560

Correct answer:

13728

Explanation:

Let us call x the smallest integer. Because the next two numbers are consecutive even integers, we can call represent them as x + 2 and x + 4. We are told the sum of x, x+2, and x+4 is equal to 72. 

x + (x + 2) + (x + 4) = 72

3x + 6 = 72

3x = 66

x = 22.

This means that the integers are 22, 24, and 26. The question asks us for the product of these numbers, which is 22(24)(26) = 13728. 

The answer is 13728.

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