PSAT Math : Decimal Operations

Study concepts, example questions & explanations for PSAT Math

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Example Questions

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Example Question #1 : Decimals

45.728 x 3.2 = ?

Possible Answers:

1463.296

14.63296

146329.6

146.3296

14632.96

Correct answer:

146.3296

Explanation:

Multiply the numbers out in long format, then move the decimal point over the total number of decimal points in the two numbers (3 in the first, 1 in the second, so 4 total):

45.728 * 3.2 = 91456

91456 + 1371840 = 1,463,296 → 146.3296

Or just count the decimal points in the answer and make sure it's 4.

Example Question #1 : How To Multiply Decimals

At the farmer's market, oranges are $0.30 each, apples are $0.25 each, bananas are $0.40 each, and tomatoes are $0.60 each. If Scott buys 3 oranges, 7 apples, 4 bananas, and 8 tomatoes, how much does he spend?

Possible Answers:

$6.80

$10.40

$7.75

$9.05

$11.40

Correct answer:

$9.05

Explanation:

To find out how much Scott spends, we need to multiply the quantity of each fruit by its price and add them all up.

3 * $0.30 + 7 * $0.25 + 4 * $0.40 + 8 * $0.60 = $9.05

Example Question #1 : Decimal Operations

If  is 25% of , what is the closest integer to the value of ?

Possible Answers:

Correct answer:

Explanation:

We can approximate the value of y pretty quickly:

y ≈ 1(0.50)(52) = 26

Since y = 0.25x = (1/4)x we know that x  = 4y ≈ 4(26) = 104

Example Question #1301 : Sat Mathematics

Possible Answers:

0.06

0.0006

0.6

0.006

6

Correct answer:

0.006

Explanation:

It's much easier to work with whole numbers, so we'll ignore the decimals for the first step: 5 x 12 = 60

Now look at the decimals. To add them back in, think of 60 as 60.0. Now move the decimal point four places to the left: 0.5 x 0.012 = .0060 = .006

 

Example Question #1 : Decimal Operations

At the store, green fabric costs $4.53 a yard. How much does 3.8 yards of green fabric cost? (Round to two decimal places.)

Possible Answers:

$17.21

$17.13

$17.12

$17.31

$17.22

Correct answer:

$17.21

Explanation:

This is a simple multiplication problem involving decimals. Simply multiply 4.53 by 3.8:

Now, round to the nearest two decimal places, giving an answer of 17.21.

Example Question #2 : Decimal Operations

Find the product. Round to the nearest hundredths place.

Possible Answers:

Correct answer:

Explanation:

The hundredths place is the position two places to the right of the decimal. Our product is . Rounding to the hundredths place results in .

Example Question #71 : Decimals

simplify: 0.2 ÷ 0.04

Possible Answers:
5
0.05
0.02
0.005
2
Correct answer: 5
Explanation:

0.2 ÷ 0.04  <- easiest way to approach is to move the decimal to the right (the same amount of spaces on each side) so that the decimal disappears

since 0.04 has 2 spaces and 0.2 only has 1, move the decimal 2 spaces to the right on each side

0.2 ÷ 0.04 = 20 ÷ 4 = 5

Example Question #1 : How To Divide Decimals

If the cost of 20 equally priced pencils cost $5.80, then at the same rate what is the greatest number of pencils you can purchase for $50?

Possible Answers:

172.41

150

172

200

173

Correct answer:

172

Explanation:

Remeber for this problem that you cannot spend more than $50. First find the price of each pencil by 5.80/20 = 29 cents. And then use this to do 50/0.29 = 172.41. So the greatest number of pencils you can purchase for $50 is 172 pencils.

Example Question #1 : Decimal Operations

Charlie has charges on his credit card of $63.70, $37.32, and $81.78. If he pays down half his bill at once, and then pays the rest in four equal monthly installments, how much is each monthly installment?

Possible Answers:

\$23.05

\$25.32

\$21.78

\$25.00

Correct answer:

Explanation:

Adding all the charges together and dividing by 2 yields $91.40. Dividing this by 4 yields a monthly installment of $22.85.

Example Question #1 : How To Divide Decimals

Simplify:

Possible Answers:

Correct answer:

Explanation:

Multiply both the numerator and denominator by some power of 10 to get rid of the decimals; in this case, multiply both by 10,000.

 

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