Two natural numbers a and b are such that a = 3b + b^2. Is 'a' a multi

Question

Two positive integers a and b are such that a = 3b + b^2. Is 'a' a multiple of 5?

(1) b is a multiple of 2

(2) b is a factor of 10

Devesh26 · Answer

a=b(3+b)
Now,
Statement 1: b is a multiple of 2. So for 2 a is multiplie of 5 but for 4 a is not multiple of 5.
So it's not a and d
Statement 2 alone
B is multiplie of 10 so b is multiplie of 5 too.
The equation becomes 10x(3+10x)
So a is always multiple of 5
Therefore b is answer

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Charli08 · Answer

1) b multiple of 2
b=2 a is then a multiple
b=4 a is not a multiple
insufficient

(2) b is a factor of 10" hence:
1:10, 2:5
not sufficient for a=1

Taking 1 and 2 together:
b multiple of 2 and factor of 10 ==> 2 and 10
a is a multiple in 5 in both those cases ===> C

stne · Answer

(1) b is a multiple of 2

if  b = 2  ans is Yes
if  b  =  4  ans is NO

INSUFF.

(2)  b  is a factor of  10

b  could be  1,2,5,10

If  b = 1   ans is No
if  b =2   ans is Yes

INSUFF.

1+2

b =2  Yes 
 b=10  Yes

SUFF.

Ans C

Two natural numbers a and b are such that a = 3b + b^2. Is 'a' a multi

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GMAT Data Sufficiency (DS) Questions

Two natural numbers a and b are such that a = 3b + b^2. Is 'a' a multi

Prep Toolkit

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