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 = $\frac{u}{v}$ = $\frac{6}{-7}$ = - $\frac{6}{7}$

thus u = - $\frac{6}{7}$ v

when v = 4, then

u = - $\frac{6}{7}$ × 4 = - $\frac{24}{7}$

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