If Y=4 when x=10 find y when x=5 write an equation to find each value

Question

If y varies directly with x write an equation for the direct variation then find each value

Answer 1

y varies directly y = kx

y/x = k

Given y =4, x = 10

It can expressed as ratio is 4/10.

We set the another ratio is y/5.

By the definition two ratios are equal.

4/10 = y/5

Multiple to each side by 5.

4/10*5 = y/5*5

20/10  = y

y = 2