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Re: a, b and c are positive integers. If b equals the square roo [#permalink]
b = sqrt of a

Means b could be 1,2,3,4,5,6,7,8,9,10 etc..

A be 1,4,9,16,25,36,49,64,81,100 etc..

30 = 25 + 5

72 = 64 + 8

Other options don’t work.
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a, band c are positive integers. If of a, and if c equals the sum of a [#permalink]
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a, band c are positive integers. If b equals the square root of a, and if c equals the sum of a and b, which of the following could be the value of c?

Indicate all such values.

A. 21
B. 30
C. 45
D. 72
E. 100
F. 331


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Re: a, band c are positive integers. If of a, and if c equals the sum of a [#permalink]
1
Stem a,b ,c = +ve
If b= (a)^(1/2)
c= a+b. b^2 =a

c= b^2+ b =b(b+1)
.: c= b(b+1) or (even)(odd) or (odd)(even)
.: c must be even and could the above
So A,C and F is out !!
Now B,D,and E ,let’s check even•odd
B (30= 3•10) (Even•odd ) yes!
D (72= 3•24) (Even•odd) yes!
E (100=5•20) (Even•odd) yes but E could also be (even)^2 (10•10)
Which is not a feature of C at all so and could never be so Out!

So B and D
Open to corrections though

Posted from my mobile device
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Re: a, band c are positive integers. If of a, and if c equals the sum of a [#permalink]
1
Can't 72 also be 2*36 in which case it would also not fulfill the requirement of C
I also had a confusion, does C only have to fulfill being even*odd or odd* even, doesnt it also have to be consecutive numbers since c=b(b+1)
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a, band c are positive integers. If of a, and if c equals the sum of a [#permalink]
I solved by plugging in numbers and got the right answer as well:

If a = 4 B = 2 C = 6, see chart below:
A B C
4 2 6
9 3 12
16 4 20
25 5 30
36 6 42
64 8 72

Only B and D are correct.
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