If x and y vary directly and yy is 70 when x is 14, find y when x is 3.

Answer 1

because x and y vary directly so y=kx

given y is 70 when x is 14 70=k*14

k=5

when x=3, y=kx=5*3=15

Answer 2

Can set up a proportion since they vary directly. Something like x₁/y₁ = x₂/y₂.

14/70 = 3/x Cross-multiply to get 14x = 210 so x = 15

Make sure the answer makes sense. If it doesn't, you've set up the proportion wrong.

Could also do 3/14 x 70, using the ratios of the two x's.