Data Sufficiency

14. If x and y are integers, is xy + 1 divisible by 3?

(1) When x is divided by 3, the remainder is 1.
(2) When y is divided by 9, the remainder is 8.

Thx

bww wrote:14. If x and y are integers, is xy + 1 divisible by 3?

(1) When x is divided by 3, the remainder is 1.
(2) When y is divided by 9, the remainder is 8.

Thx

Is it C ?

1 - insufficient. x = 3t+1.
[ (3t+1)*y + 1 ] / 3
= (3ty + y + 1) / 3

So, divisibility depends on the value of y

2 - insufficient. y = 9s + 8
(xy + 1) / 3
= (9sx + 8x + 1) / 3

Again, depends on value of x

Together,

(3t+1)*(9s+8 ) + 1
= 27ts + 9s + 24t + 8 + 1
= 27ts + 9s + 24t + 9

All the terms above are divisible by 3 and hence is sufficient.

yes, OA is C

thx