If x=8y+11 then which of the following cannot be a divisor

Question

If x=8y+11 then which of the following cannot be a divisor of x. (y is a whole number)?

(A)3
(B)5
(C)7
(D)12

vishnuns39620 · Answer

I think the answer is Option D "12".

Reasoning :-

A quick way to approach this problem is to see the x=8y + 11 equation & trying to quickly substituting values for "y"; If you plug in y=-1, -2, 3 you can easily see they are respectively divisible by 3, 5 & 7. But in each case, the final value of "x" will be odd due to the addition of 11 to a multiple of 8 (due to 8y). Hence, you can never have an even divisor for "x".

Thus option D (12) is the one that can not be a possible divisor for x. In hindsight, you can see that this boils down to a simple remainder problem, one where you can easily guess the answer based on the fact that x will always be "odd" and hence not divisible by an even number.

Hope it helps!

clearwater · Answer

I think D.

X =8y + 11. will always be a odd number as 8y is always even and 11 is odd, and sum of even and odd integer is odd. Now an odd integer cannot be perfectly divisible an even number. Of all the options only 12 is an even number.

igotthis · Answer

I think its D. 
Since x = 8y+11 and y is a whole number, y must be even since 8y = even
Therefore even + odd = odd
Since x is odd, you cannot have an even divisor of x. 12 is the only even number on the list

unceldolan · Answer

You can find the solution by eliminating the choices.

Multiples of 8: 0,8,16,24,32,40,48,56,64,72,80...
(1) Plug in 2 for y, then 8*2 + 11 = 27 which is divisible by 3 --> out
(2) Plug in 3 for y, then 8*3 + 11 = 35 which is divisible by 5 --> out
(3) Plug in 10 for y, then 8*10 + 11 = 91 which is divisible by 7 --> out

Only answer left is D.

Konstantin1983 · Answer

This question is incomplete. Where is option E?))

MarkusKarl · Answer

X=8y+11.
X=odd.
Even integers cant divide odd numbers.
Only 12 is odd among the answer choices.
D

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abhimahna · Answer

How does that matter if we have the answer in one of the options given? :-D

Konstantin1983 · Answer

This increases the probability to guess this question correct :-D

KanishkM · Answer

x = 8y+11

Start plugging in values for y at 0,1,2,3,4,5,6,7

x = 11,19,27,35,43,51,59

Except 12 all 3 gets consumed by x

D

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If x=8y+11 then which of the following cannot be a divisor

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If x=8y+11 then which of the following cannot be a divisor

Prep Toolkit

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