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# If 25 percent of a certain number is 1,600, what is 10 percent of the

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Math Expert
Joined: 02 Sep 2009
Posts: 51229
If 25 percent of a certain number is 1,600, what is 10 percent of the  [#permalink]

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26 Jun 2018, 04:07
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5% (low)

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95% (00:45) correct 5% (00:00) wrong based on 49 sessions

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If 25 percent of a certain number is 1,600, what is 10 percent of the number?

(A) 40

(B) 400

(C) 640

(D) 1,440

(E) 4,000

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Re: If 25 percent of a certain number is 1,600, what is 10 percent of the  [#permalink]

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26 Jun 2018, 04:13

Solution

Given:
• 25% of a certain number is 1600

To find:
• The value of 10% of that number

Approach and Working:
If we assume the number to be n,
• 25% of n = $$\frac{n}{4}$$ = 1600
Or, n = 1600 * 4

• Therefore, 10% of n = 1600 * 4 * $$\frac{10}{100}$$ = 160 * 4 = 640

Hence, the correct answer is option C.

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Re: If 25 percent of a certain number is 1,600, what is 10 percent of the  [#permalink]

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26 Jun 2018, 04:21
Bunuel wrote:
If 25 percent of a certain number is 1,600, what is 10 percent of the number?

(A) 40

(B) 400

(C) 640

(D) 1,440

(E) 4,000

In these question, it's helpful to know
5%=1/20
10%=1/10
12 1/2=1/8
25%= 1/4
33 1/3=1/3
50=1/2
75=3/4..
And so on

Here 25%=1/4..
So if 1/4 is 1600, so number is 1600*4
Therefore 10% will be 1600*4/10=640
C
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Re: If 25 percent of a certain number is 1,600, what is 10 percent of the  [#permalink]

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26 Jun 2018, 08:32
Bunuel wrote:
If 25 percent of a certain number is 1,600, what is 10 percent of the number?

(A) 40

(B) 400

(C) 640

(D) 1,440

(E) 4,000

25 percent of a certain number is 1,600

So, 100 percent of a certain number is 6,400

Now, 10 percent of 6,400 = 640, Answer must be (C)
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If 25 percent of a certain number is 1,600, what is 10 percent of the  [#permalink]

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26 Jun 2018, 12:20
This is an easy one by normal method.

Just to try a different approach

25% of a number = 1600

10% of a number = (25% of a number)/2 = 12.5% approximately = 1600/2 = 800 approx

Number should be close to 800 (preferably on the lower side)

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Re: If 25 percent of a certain number is 1,600, what is 10 percent of the  [#permalink]

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26 Jun 2018, 14:13
Bunuel wrote:
If 25 percent of a certain number is 1,600, what is 10 percent of the number?

(A) 40

(B) 400

(C) 640

(D) 1,440

(E) 4,000

The number $$10$$ is $$\frac{2}{5}$$th of $$25$$. The same rule will apply to percentages.

Therefore, if 25% of a certain number is 1600, then 10% of this number is $$\frac{2}{5}*1600$$ = 640(Option C)

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Re: If 25 percent of a certain number is 1,600, what is 10 percent of the  [#permalink]

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27 Jun 2018, 17:11
Bunuel wrote:
If 25 percent of a certain number is 1,600, what is 10 percent of the number?

(A) 40

(B) 400

(C) 640

(D) 1,440

(E) 4,000

We can let n = the number in question and create the equation:

0.25n = 1,600

n = 6,400

So 10% of 6,400 is 0.1 x 6,400 = 640.

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Re: If 25 percent of a certain number is 1,600, what is 10 percent of the &nbs [#permalink] 27 Jun 2018, 17:11
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