y = 8
Find an equation of variation where y varies directly as x. One pair of values is y = 80 when x = 40
40
y = -5
y = kx: 10 = 37k so k = 10/37 and y = 10x/37
If P varies directly with q, r and s then P = kqrs, where k is a constant. As 70 = k x 7 x 5 x 4 = 140k : k = 70/140 = 1/2 The equation of joint variation is P = ½qrs.
Find an equation of variation where y varies directly as x. One pair of values is y = 80 when x = 40
y = 10x
4x= y
a varies directly as b and a = 12 when b = 4. What is the constant of variation?
57
40
y = -5
y = 3x y = 3*19 = 57
direct variation: y = kx y = kx k = y/x = 0.8/0.4 = 2
y = kx: 10 = 37k so k = 10/37 and y = 10x/37
2
1