Which of the following best approximates the value of q if

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Director

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Which of the following best approximates the value of q if [#permalink]

01 Nov 2007, 16:06

Which of the following best approximates the value of q if 528+311=5q ?

39
30
28
27
17
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01 Nov 2007, 16:17

Are you sure there isn't a typo here?

q is > 100

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Correction --- [#permalink]

01 Nov 2007, 16:17

Which of the following best approximates the value of q if 5^28+3^11=5^q ?

39
30
28
27
17
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01 Nov 2007, 16:19

A. 39 is the best approx.

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01 Nov 2007, 16:19

Which of the following best approximates the value of q if 5^28+3^11=5^q ?

39
30
28
27
17

My quick and dirty would be;

since 5 ^28 + 3 ^ 11 > 5 ^28 therefore the answer could be either 30 or 39

I would go with 30.
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01 Nov 2007, 16:20

any more clues to get to the right answer without doing any calculations?
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Re: Math - MGMT [#permalink]

01 Nov 2007, 16:22

alimad wrote:

Which of the following best approximates the value of q if 528+311=5q ?

39
30
28
27
17

From what I remember from these type of problems, you should completely ignore the 3^11.

So in that case q is equal to aprox. 28

C.

If not C then B, sry said D when I meant B.

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Re: Correction --- [#permalink]

01 Nov 2007, 19:10

alimad wrote:

Which of the following best approximates the value of q if 5^28+3^11=5^q ?

39
30
28
27
17

NOTE:
GMAT doesnt test your LOGARITHMS skill

Taking logs on both sides

28*log5 + 11*log3 = q*log5

Dividing by log5 throughout

28 + 12(appx) = q

12 appx 'cos loga to base a is 1 but if base is <a>1

Should be 39(appx)

Last edited by trivikram on 01 Nov 2007, 19:30, edited 2 times in total.

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Re: Correction --- [#permalink]

01 Nov 2007, 19:26

alimad wrote:

Which of the following best approximates the value of q if 5^28+3^11=5^q ?

39
30
28
27
17

here is my take on the problem:

5^28+3^11=5^q
can be written in this way
5^28 + 3^3 * 3^3 * 3^2 = 5^q
3^3 = 27 close to 5^2, so...
5^28 + 5^2 * 5^2 * 3^2 = 5^q
so it's really 5^28 + 5^4 * 9 = 5^q
so answer is 5^28 + 625*9 (approx)
625*9 does not make a great impact when added to 5^28

i say the answer is q = 28
whats the OA??

Re: Correction --- [#permalink] 01 Nov 2007, 19:26

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Which of the following best approximates the value of q if

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Which of the following best approximates the value of q if

Which of the following best approximates the value of q if

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