Question

If y varies directly as x and y = 21 when x = 5, find x when y = 42.

Answer 1

Answer: 10

Explanation:

varies directly means:
`(y)/(x) = k`

Step 1: solve for k ⇒
`(21)/(5) = k`

Step 2: plug in the given value and k to solve for the missing value:
`(42)/(x) = (21)/(5)`

42(5) = 21(x)

`(42(5))/(21) = (21(x))/(21)`

2(5) = x

10 = x