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Root of (16*20+8*32)=

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Root of (16*20+8*32)= [#permalink] New post 03 Sep 2012, 05:00
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78% (02:03) correct 22% (01:52) wrong based on 473 sessions
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Re: Root of (16*20+8*32)= [#permalink] New post 03 Sep 2012, 05:01
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Re: Root of (16*20+8*32)= [#permalink] New post 03 Sep 2012, 05:14
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\sqrt{16*20+8*32}=\sqrt{16*(1*20+8*2)}=4*\sqrt{36}=4*6=24

Answer B.
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Re: Root of (16*20+8*32)= [#permalink] New post 03 Sep 2012, 06:56
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\sqrt{4*4*4*5 + 4*4*4*4} = 2*2*2\sqrt{5+4} = 8*\sqrt{9} = 8*3 = 24

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Re: Root of (16*20+8*32)= [#permalink] New post 04 Sep 2012, 02:39
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\sqrt{576} = 24
B is the right answer.
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Re: Root of (16*20+8*32)= [#permalink] New post 07 Sep 2012, 04:23
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Re: Root of (16*20+8*32)= [#permalink] New post 14 Oct 2012, 07:05
Obviously I don't get this..... :shock:

I know this must be wrong since no answer choice allows this, but where am I mistaking? Appreciate the help!

Rt (16*20)+(8*32)=
Rt(2^4*2^2*5)+(2^3*2^5)=
2^3 Rt(5)+2^4=
8Rt5+16 ??
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Re: Root of (16*20+8*32)= [#permalink] New post 14 Oct 2012, 22:47
Quote:
Obviously I don't get this.....

I know this must be wrong since no answer choice allows this, but where am I mistaking? Appreciate the help!

Rt (16*20)+(8*32)=
Rt(2^4*2^2*5)+(2^3*2^5)=
2^3 Rt(5)+2^4=
8Rt5+16 ??


If you find the shortcuts difficult then take the longer method, by which you can still solve it under the recommended time ...


We are to find the Root of 16x20 + 8x32..

16x20 = 320 , and 32 x 8 = 256 .. Adding them we get , 576 So we are to find the root of 576...

4 root 20 cannot be equal to 576 ( in order to get 576 from this root of 20 would have to be 144 which is obviously not possible) SO A IS OUT ..

24 . Multiplying 24 by 24 we get 576 therefore b is the correct answer..
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Re: Root of (16*20+8*32)= [#permalink] New post 15 Oct 2012, 02:02
Expert's post
asveaass wrote:
Obviously I don't get this..... :shock:

I know this must be wrong since no answer choice allows this, but where am I mistaking? Appreciate the help!

Rt (16*20)+(8*32)=
Rt(2^4*2^2*5)+(2^3*2^5)=
2^3 Rt(5)+2^4=
8Rt5+16 ??


It should be:

\sqrt{16*20+8*32}=\sqrt{2^4*2^2*5+2^3*2^5}=\sqrt{2^6*5+2^8}=\sqrt{2^6(5+2^2)}=\sqrt{2^6*9}=2^3*3=24.

Hope it's clear.
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Re: Root of (16*20+8*32)= [#permalink] New post 15 Oct 2012, 10:12
asveaass wrote:
Obviously I don't get this..... :shock:

I know this must be wrong since no answer choice allows this, but where am I mistaking? Appreciate the help!

Rt (16*20)+(8*32)=
Rt(2^4*2^2*5)+(2^3*2^5)=
2^3 Rt(5)+2^4=
8Rt5+16 ??


Check highlighted portion, when u took out 2^3 , outside the root, basically you left inside only 2^2. However in highlighted portion, you marked it as 2^4 and hence the wrong answer.
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Re: Root of (16*20+8*32)= [#permalink] New post 25 Mar 2014, 01:19
Factor out 64 which is a perfect square

\sqrt{64 * (5 + 4)}

\sqrt{64 * 9}

8 * 3 = 24 = Answer = B
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Re: Root of (16*20+8*32)= [#permalink] New post 16 Nov 2014, 08:11
Rt(16*20)+(8*32) = Rt(4*4*2*10)+(4*2*4*8)= Rt(4^2*2*10)+(4^2*2*8)= 4*Rt(2*10+2*8)= 4*Rt(36)= 4*Rt(6^2)= 4*6=24
Re: Root of (16*20+8*32)=   [#permalink] 16 Nov 2014, 08:11
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