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# square root of 4 x 9 + 9 x 16 / 25 0 18/5 0 12/sq.

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Intern
Joined: 19 Nov 2004
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square root of 4 x 9 + 9 x 16 / 25 0 18/5 0 12/sq. [#permalink]  19 Dec 2004, 17:52
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15. square root of 4 x 9 + 9 x 16 / 25

0 18/5
0 12/sq. root of 5
0 3 * sq. root of 26 / 5
0 2 *sq. root of 3 / 5
0 6 / sq. root of 5
Manager
Joined: 19 Nov 2004
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[#permalink]  21 Dec 2004, 13:30
sqrt(4x9+9x16/25)=sqrt(4x9)sqrt(1+4/25)=6/5 x sqrt(29)
and this is the answer
Manager
Joined: 13 Dec 2004
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[#permalink]  21 Dec 2004, 20:28
sqrt(4x9+9x16/25)=sqrt(4x9)sqrt(1+4/25)=6/5 x sqrt(29)
and this is the answer[/quote]

Can you explain how you got to that sqrt(4x9+9x16/25)=sqrt(4x9)sqrt(1+4/25) ???
Manager
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[#permalink]  21 Dec 2004, 23:18
I can!
sqrt(4x9+9x16/25)=sqrt(4x9+9x4x4/25)=sqrt(4x9x(1+4/25))=sqrt(4x9)xsqrt(1+4/25)=2x3xsqrt(25/25+4/25)=6xsqrt(29/25)=6xsqrt(29)/sqrt(25)=(6/5)xsqrt(29)
Did I miss something
Manager
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[#permalink]  22 Dec 2004, 10:03
Okay, so when you get to this:

sqrt(36(1+4/25)

I see how you can pull the 36 out, but how do you pull the 1/25 out? It looks like you multiplied the 1 by 25--which is why root 29 is in your final answer--and that you pulled (1/5) out, which is why your coefficient is 6/5. Right? But I don't understand how you can do that. Maybe this is too difficult to explain in this forum, sorry if the answer is obvious but I'm really confused.
Director
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[#permalink]  22 Dec 2004, 17:33
I get E. 6/sqrt(5)

I think by 4 x 9 + 9 x 16 / 25 you mean (4x9 + 9x16) *1/25...
CIO
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[#permalink]  24 Dec 2004, 00:15
gayathri wrote:
I get E. 6/sqrt(5)

I think by 4 x 9 + 9 x 16 / 25 you mean (4x9 + 9x16) *1/25...

agreed. the answer is E the way I read it, too.
Manager
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[#permalink]  24 Dec 2004, 13:48
I can't get from 6 sqrt [(1 + 4/25)] to 6 over root 5.
Director
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[#permalink]  25 Dec 2004, 18:05
hilairity wrote:
I can't get from 6 sqrt [(1 + 4/25)] to 6 over root 5.

Hilairity, I think there is a typo in the question. I think the denominator 25 applies to both the terms 4x9 and 9x16
Manager
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[#permalink]  27 Dec 2004, 10:42
Guys,

Remember that sqrt (a+b) does not equal to sqrt a + sqrt b. They are not the same. I made that mistake initially. Write out the sqrt when you solve that question
[#permalink] 27 Dec 2004, 10:42
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# square root of 4 x 9 + 9 x 16 / 25 0 18/5 0 12/sq.

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