If m and n are positive integers and m^2 + n^2 = 40, what is

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If m and n are positive integers and m^2 + n^2 = 40, what is [#permalink]

01 Nov 2012, 07:56

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85% (02:17) correct

14% (01:01) wrong

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If m and n are positive integers and m^2 + n^2 = 40, what is the value of m^3 + n^3?

A. 72
B. 224
C. 320
D. 512
E. 1,600

Pls try algebra method...
Of course, plugging nos easily gives 2 and 6(m and n being integers), but i attempted algebra first
and was wasting time.

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Last edited by Bunuel on 01 Nov 2012, 08:01, edited 1 time in total.

Renamed the topic and edited the question.

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Re: If m and n are positive integers and m^2 + n^2 = 40, what is [#permalink]

01 Nov 2012, 12:16

Hey,

i have tried it this way:

You need to integers which squared are equal 40.

Which could it be ? Let's start with the first integer:

1^2 = 1
2^2 = 4
3^2 = 9
4^2 = 16
5^2 = 25
6^2 = 36
Stop. The integers can't be greater than 6 or we will score above 40.

The second integer need to be picked up the same way.
1^2 = 1
2^2 = 4
3^2 = 9
4^2 = 16
5^2 = 25
6^2 = 36

The only pair that matches is 6^2 + 2^2 = 40.

So 6^3 + 2^3 = 224.

Answer b.)

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Re: If m and n are positive integers and m^2 + n^2 = 40, what is [#permalink]

10 Dec 2012, 23:35

I tried algebraic method. I think it will eat up my life in the test. Haha! Nonetheless, I would like to see how that is done.

I just selected from the possible values of m^2 and n^2: 1,4,9,16,25,36 and selected 2^2 and 6^2

m^3 + n^3=2^3 + 6^3 = 224

Re: If m and n are positive integers and m^2 + n^2 = 40, what is [#permalink] 10 Dec 2012, 23:35

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If m and n are positive integers and m^2 + n^2 = 40, what is

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If m and n are positive integers and m^2 + n^2 = 40, what is

If m and n are positive integers and m^2 + n^2 = 40, what is

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