Problem Solving

Hi All,

We're told that X and Y are INTEGERS, when X is divided by 2, the remainder is 1 and when Y is divided by 8, the remainder is 2. We're asked which answer COULD be the value of 2X + Y. This question can be solved by TESTing VALUES.

Since X/2 has a remainder of 1, then X must be ODD: 1, 3, 5, 7, 9, 11, etc.
This means that 2X will be EVEN (but not every even number is possible): 2, 6, 10, 14, 18, 22.....

Since Y/8 has a remainder of 2, Y could be.... 2, 10, 18, 26, etc.

The answer choices are relatively small, so we should be looking at the smaller possibilities for 2X and Y. Two possibilities lead to the same correct answer:
IF.... 2X = 2 and Y = 10, then (2X + Y) = 12
IF.... 2X = 10 and Y = 2, then (2X + Y) = 12

Final Answer: C

GMAT assassins aren't born, they're made,
Rich

BTGmoderatorLU wrote: Source: GMAT Prep

When x is divided by 2, the remainder is 1 and y is divided by 8, the remainder is 2. Which of the following
could be the value of 2x + y? (x and y are integers)

A. 10
B. 11
C. 12
D. 13
E. 14

We see that x could be 1, 3, 5, etc. and y could be 2, 10, 18, etc. We see that x is odd and y is even, so 2x + y is even. Since 2(1) + 10 = 12, we see that 2x + y could be 12.

Alternate Solution:

Since the remainder when x is divided by 2 is 1, x can be expressed as x = 2p + 1 for some integer p. Similarly, since the remainder when y is divided by 8 is 2, y can be expressed as y = 8q + 2 for some integer q. Then, multiplying the first equality by 2 and adding the result to the second equality, we obtain:

2x + y = 4p + 8q + 4

We notice that each of the terms 4p, 8q and 4 are divisible by 4, therefore 2x + y must be divisible by 4. The only answer choice that is divisible by 4 is 12.

Answer: C