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# Jack was asked by her teacher to subtract 3 from a certain number and

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Jack was asked by her teacher to subtract 3 from a certain number and  [#permalink]

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10 Nov 2018, 10:06
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Difficulty:

15% (low)

Question Stats:

97% (01:12) correct 3% (02:07) wrong based on 34 sessions

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GMATbuster's Weekly Quant Quiz#8 Ques #3

Jack was asked by her teacher to subtract 3 from a certain number and then divide the result by 9. Instead, she subtracted 9 and then divided the result by 3, giving an answer of 43. What would her answer have been had she worked the problem correctly?

A) 15
B) 34
C) 43
D) 51
E) 138

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Re: Jack was asked by her teacher to subtract 3 from a certain number and  [#permalink]

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10 Nov 2018, 10:10
Working backwards
43*3+9=138

Now 138-3=135/9=15

Hence ans=15 A
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Re: Jack was asked by her teacher to subtract 3 from a certain number and  [#permalink]

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10 Nov 2018, 10:11
Answer is option A: i.e. 15
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Re: Jack was asked by her teacher to subtract 3 from a certain number and  [#permalink]

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10 Nov 2018, 10:12
Let the certain number be x.

Now the correct way is (x-3)/9
but she did (x-9)/3 and got 43
Then x = 138
substituting this in (x-3)/9 = 135/9 = 15

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Re: Jack was asked by her teacher to subtract 3 from a certain number and  [#permalink]

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10 Nov 2018, 10:12
(x-9)/3 =43
So, x = 138.

Using x in:
(x-3)/9
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Re: Jack was asked by her teacher to subtract 3 from a certain number and  [#permalink]

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10 Nov 2018, 10:13
Let the number be x.

Now Jack subtracted 9 from the the number and then divided by 3 to result in 43.
This can be written as : (x-9)/3=43
=> x-9=129
=> x=138.

So, the number is 138 and Jack was asked to subtract 3 and divide by 9.
Her correct answer should have been => (x-3)/9 = (138-3)/9 = 135/9 = 15.

Hence, A) 15.
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Re: Jack was asked by her teacher to subtract 3 from a certain number and  [#permalink]

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10 Nov 2018, 10:14
1
Say the actual number was x .
So 43*3+9 = x
or x=138

SO, in the correct way the result should have been = (138-3)/9 =135/9 = 15 Hence , Ans A
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Re: Jack was asked by her teacher to subtract 3 from a certain number and  [#permalink]

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10 Nov 2018, 10:23
(X-9) / 3 = 43

X= 129 + 9 = 138

(X-3) / 9 = 135 / 9 = 15

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Re: Jack was asked by her teacher to subtract 3 from a certain number and  [#permalink]

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10 Nov 2018, 10:29
1
she did the following to the original number X

=$$\frac{(X-9)}{3=43}$$

=$$x-9=129$$

=$$x=138$$

The actual calculation was
=$$\frac{(X-3)}{9}$$

=$$\frac{(135)}{9}$$

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Re: Jack was asked by her teacher to subtract 3 from a certain number and  [#permalink]

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10 Nov 2018, 10:30
Let x be the number
Intended calculation
(x-3)/9
Performed calculation=43
(x-9)/3=43
x=138

sub x in intended calculation
(x-3)/9 = (135/9)=15

option A
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Re: Jack was asked by her teacher to subtract 3 from a certain number and  [#permalink]

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10 Nov 2018, 11:02
let the number be x

(x-9)/3=43
x=138

As per correct calculation , it should be (x-3)/9 = 135/9=15
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Re: Jack was asked by her teacher to subtract 3 from a certain number and  [#permalink]

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11 Nov 2018, 00:34
=> x - 3/9 = 43
=> x - 9 = 129
=> x = 129 + 9
=> x = 138

138 - 3 = 135/9 = 15

Re: Jack was asked by her teacher to subtract 3 from a certain number and   [#permalink] 11 Nov 2018, 00:34
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