Carcass wrote:
If x = (y)(y + 1) and y is a prime number less than 11, which of the following could not be the product of 2 consecutive integers?
a) 5x
b) 11x
c) 13x
d) 23x
e) 57x
Since y is a prime number less than 11, there are only 4 possible vales for y.
y COULD equal 2, 3, 5 or 7
This also means there are only 4 possible vales for x.
x = (y)(y + 1)If y = 2, then x = (2)(2 + 1) =
6If y = 3, then x = (3)(3 + 1) =
12If y = 5, then x = (5)(5 + 1) =
30If y = 7, then x = (7)(7 + 1) =
56Now let's check each answer choice...
a) Can 5x be the product of 2 consecutive integers?
Yes. When x =
6, then 5x = 5(
6) = 30
So, 5x CAN BE the product of 2 consecutive integers (5 and 6)
ELIMINATE A
b) Can 11x be the product of 2 consecutive integers?
Yes. When x =
12, then 11x = 11(
12)
So, 11x CAN BE the product of 2 consecutive integers (11 and 12)
ELIMINATE B
c) 13x
When x =
12, then 13x = 13(
12)
So, clearly, 13x CAN BE the product of 2 consecutive integers (12 and 13)
ELIMINATE C
e) 57x
When x =
56, then 57x = 57(
56)
So, clearly, 57x CAN BE the product of 2 consecutive integers (56 and 57)
ELIMINATE E
By the process of elimination, the correct answer is D
Cheers,
Brent