if x + y is divisible by 0, which of the following expressions must also be divisible by:
a. x/y + 9
b. (9x) + y
c. x + (9y)
d. xy + 9
e. 2x + 2y
3 answers
SORRY I MEANT DIVISIBLE BY 9 NOT 0
look at e)
2x + 2y = 2(x+y)
but x+y is divisible by 9, so would be any multiple of x+y
what about the others.
All we need is one case where the statement would be false, and we can rule out that choice.
let x=2, y = 7, clearly x+y is divisible by 9
a) 2/7 + 9 divisible by 9? NO
b) 9(2) + 7 = 25 , NO
c) 2 + 9(7) = 65 , NO
d) (2)(7) + 9 = 23, NO
looks like e) is it.
btw, for a number to be divisible by 9, the sum of its digits will be divisible by 9
2x + 2y = 2(x+y)
but x+y is divisible by 9, so would be any multiple of x+y
what about the others.
All we need is one case where the statement would be false, and we can rule out that choice.
let x=2, y = 7, clearly x+y is divisible by 9
a) 2/7 + 9 divisible by 9? NO
b) 9(2) + 7 = 25 , NO
c) 2 + 9(7) = 65 , NO
d) (2)(7) + 9 = 23, NO
looks like e) is it.
btw, for a number to be divisible by 9, the sum of its digits will be divisible by 9
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