Question

1. Suppose y varies directly with x, and y = 14 when x = –4. What is the value of y when x = –6?

–21
10
18
21

2. Suppose y varies directly with x, and y = 25 when x = 140. What is the value of x when y = 36?

140
165
201.6
176

3. The point (12, 9) is included in a direct variation. What is the constant of variation?

one half
three fourths
1
2

Answer 1

1) y varies directly with x, then we have: y = kx, k is the constant of variation

y = kx

14 = - 4k
k = 14/- 4, or - 7/2, or - 3.5

y = kx
y = - 3.5(- 6)
y=21

2) 201.6 is the right answer.see the procedure used in Q1.

3) K = y/x
= 9/12
= 3/4