If 18 is 15 percent of 30 percent of a certain number, what is the number?

Let X be the number we want

We are given 18 is 15% of 30% of the number we want.
We can write an equation using this in the form:
$$\frac{15}{100}\cdot\frac{30}{100}\cdot X=18$$
$$\frac{450}{10000}\cdot X=18$$
$$\frac{45}{1000}\cdot X=18$$
$$\frac{9}{200}\cdot X=18$$
$$\frac{1}{200}\cdot X=2$$
Therefore,
$$X=400$$

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Re: If 18 is 15 percent of 30 percent of a certain number, what is the number?

by Scott@TargetTestPrep » Mon Aug 31, 2020 10:36 am

BTGmoderatorLU wrote: ↑
Thu Aug 27, 2020 2:53 pm
Source: GMAT Paper Tests

If 18 is 15 percent of 30 percent of a certain number, what is the number?

A. 9
B. 36
C. 40
D. 81
E. 400

The OA is E

Solution:

Letting x = the certain number, we can create the equation:

18 = 0.15 * 0.3 * x

18 = 0.045x

18000 = 45x

x = 18000/45 = 400

Answer: E

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