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If a is a positive integer and y = 3.2 x 10^a, what is the value of y?

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If a is a positive integer and y = 3.2 x 10^a, what is the value of y?  [#permalink]

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29 Dec 2017, 09:17
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45% (medium)

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57% (01:34) correct 43% (01:20) wrong based on 43 sessions

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If a is a positive integer and $$y = 3.2$$ x $$10^a$$, what is the value of y?

1. $$400 < y < 30,000$$

2. $$y^2$$ $$=$$ $$1.024$$ x $$10^7$$

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If a is a positive integer and y = 3.2 x 10^a, what is the value of y?  [#permalink]

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29 Dec 2017, 09:28
QZ wrote:
If a is a positive integer and $$y = 3.2$$ x $$10^a$$, what is the value of y?

1. $$400 < y < 30,000$$

2. $$y^2$$ $$=$$ $$1.024$$ x $$10^7$$

Statement I 400<y<30,000 has only 3200 in the range..
320 is less and 32000 is more, so y =3200
Sufficient

Statement II..
Don't waste time in calculating value of y..
Here y will have two values one POSITIVE and other NEGATIVE..
But we are looking for only POSITIVE..
So sufficient

D
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1) Absolute modulus : http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
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3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html

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Re: If a is a positive integer and y = 3.2 x 10^a, what is the value of y?  [#permalink]

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29 Dec 2017, 09:32
QZ wrote:
If a is a positive integer and $$y = 3.2$$ x $$10^a$$, what is the value of y?

1. $$400 < y < 30,000$$

2. $$y^2$$ $$=$$ $$1.024$$ x $$10^7$$

Statement 1: $$a$$ cannot be $$1$$ or $$2$$ because in that case $$y=32$$ or $$320 <400$$ not possible

$$a$$ cannot be $$4$$ because in that case $$y=32000>30000$$ not possible

so $$a=3$$ hence $$y=3.2*10^3$$. Sufficient

Statement 2: we know $$a$$ is positive so $$y>0$$

Take the square root of $$y^2$$ and as negative value of $$y$$ is not possible so we have only one value for $$y$$. Sufficient

Option D
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Re: If a is a positive integer and y = 3.2 x 10^a, what is the value of y?  [#permalink]

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29 Dec 2017, 09:39
QZ wrote:
If a is a positive integer and $$y = 3.2$$ x $$10^a$$, what is the value of y?

1. $$400 < y < 30,000$$

2. $$y^2$$ $$=$$ $$1.024$$ x $$10^7$$

This is a "stolen" OG question: https://gmatclub.com/forum/if-n-is-a-po ... 26370.html
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Re: If a is a positive integer and y = 3.2 x 10^a, what is the value of y? &nbs [#permalink] 29 Dec 2017, 09:39
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