Question

Y varies inversely with x and when x = 7, y = 15. Find x when y = 21

x=​

Answer 1

x = 5

Explanation:

Use the inverse variation equation, y = k/x

Plug in 7 as x and 15 as y, then solve for k:

y = k/x

15 = k/7

105 = k

So, the equation is y = 105/x

Find x when y = 21 by plugging in 21 as y:

y = 105/x

21 = 105/x

21x = 105

x = 5

So, when y = 21, x = 5