Question

If u varies directly with v and u=6 when v= -7, what is u when v=4. Show steps.

Answer 1

Since u varies directly with v, then

u = kv ( k is the constant of variation )

to find k use u = 6 when v = - 7

k =
`(u)/(v)` =
`(6)/(-7)` = -
`(6)/(7)`

thus u = -
`(6)/(7)` v

when v = 4, then

u = -
`(6)/(7)` × 4 = -
`(24)/(7)`

Answer 2

direct variation

u=kv

6=k(-7)

k=-6/7

u=kv

u =-6/7 * 4

u =-24/7

Answer: u = -24/7 or -3 3/7