How to multiply decimals

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GRE Quantitative Reasoning › How to multiply decimals

Questions 1 - 4
1

Given that , which best describes the relationship between , , and ?

Explanation

We must recognize that if x and y are both between 0 and 1, then they must be fractions (decimals). To determine their relationships, we can substitute values for x and y. Let's have and (because y must be greater than x).

If x and y are both between 0 and 1, then xy is also between 0 and 1 (though smaller than either x or y individually).

The value of (xy)2 will be less than (xy), since squaring any number between 0 and 1 gives a smaller result.

Finally, is largest, since dividing a larger number by a smaller one gives a result greater than 1.

Note that the substituted values for x and y were purely hypothetical; any values that satisfy the given inequality could be used.

2

There are 3,500 people in group A and 5,000 people in group B:

Car Type% in Group A Who Own% in Group B Who Own
Motorbike49
Sedan3525
Minivan2215
Van912
Coupe36

The number of people in group B who own a minivan is how much greater or less than the number of people in group A who own a minivan?

50 fewer

30 fewer

15 more

20 fewer

30 more

Explanation

In this question, simply take the percentage of each group that owns a minivan and compare the values. For minivans we look at the middle row which we recognize as a percent that must be converted to a decimal. Acknowledge that there's a different number of people between the groups A and B:

Group B: 0.15(5000) = 750

Group A: 0.22(3500) = 770

750 – 770 = –20; thus, group B has 20 fewer people who own minivans than group A.

3

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:

4

find 0.72

0.0049

49

4.9

0.49

0.049

Explanation

0.7 * 0.7 = 0.49

Trick: do the numbers without the decimals (7*7)

49; move the decimal of the answer the total number of spaces per each number (one for each 0.7)

0.49

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