How to multiply decimals

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SAT Math › How to multiply decimals

Questions 1 - 5
1

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

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

2

45.728 x 3.2 = ?

146.3296

1463.296

14632.96

146329.6

14.63296

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.

3

6

0.6

0.06

0.006

0.0006

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

4

You bought a dozen eggs marked at and received change from . What is the percent of sales tax?

Explanation

Set the equation up as

Solve for , which equals

or

Therefore the percent sales tax is:

5

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?

$9.05

$10.40

$6.80

$7.75

$11.40

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

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