Suppose y varies directly as x, and Y=80 when X=16. Which of the following statements is true?
A.The constant of variation is 5.
B.The variable y does not vary directly with x.
C.The constant of variation is -5.
D.The constant of variation is 1 over 5

Question

Suppose y varies directly as x, and Y=80 when X=16. Which of the following statements is true?
A.The constant of variation is 5.
B.The variable y does not vary directly with x.
C.The constant of variation is -5.
D.The constant of variation  is 1 over 5

jim_thompson5910 · Answer

"Suppose y varies directly as x" means that y = kx 

where k is some fixed constant

jim_thompson5910 · Answer

y = kx

80 = k*16 ... plug in x = 16 and y = 80

k = ???