Posted by Mark Russel on .
DIRECT VARIATION
1. a is directly proportional to b.If a=15,then b=9
2. m varies directly as n.If n=2/3,then m=1/4
3. T varies as the square root of L. If L=81,then T=10
4.r varies directly as the square of t. If t=16,then r=6.
5. y varies as the cube foot of x. If x=27,then y=2.
6. y is directly proportional to x. If y=15 when x=4,find y when x=5.
7. m varies directly as n. If m= 6 when n=2,find m when n=3
8. The square of x varies directly as the cube of y. When x=2,y=4,find y when x=8

Math 
Reiny,
What do you want for #1  5 ?
Are you finding the constant of variation or what?
I will do one of them, #4
r varies directly as the square of t. > r = kt^2
when t=16, r=6
6 = k(16)^2
6 = 256k
k = 6/256 = 3/128
so r = (3/128)t^2
#8.
The square of x varies directly as the cube of y. > x^2 = ky^3
when x=2, y=4
4 = k(64)
k = 4/64 = 1/16
so x^2 = (1/16)y^3
when x = 8
64 = (1/16)y^3
y^3 = 1024
y = 1024^(1/3) = 8cuberoot(2)
Do the others the same way.
let me know what you got for the rest.