If y varies directly as x, and y is 6 when x is 72, what is the value of y when x is 8?

Solution:

Given: y varies directly as x. So has the direct variation.

y = k × x ---> eq(1) where k is the constant of proportionality

Here k be a non-zero constant variation. Let us evaluate for 'k'.

x = 72 when y = 6

Substitute the values of x and y in the equation(1)

6 = k × 72

k = 6/72

= 1/12

The equation of variation is y = (1/12) × x

To find y when x = 8,

Substitute x = 8 in the equation of variation.

y = (1/12) × 8

y = 2/3

---

If y varies directly as x, and y is 6 when x is 72, what is the value of y when x is 8?

Summary:

If y varies jointly as x, the value of y will be 2/3., when x = 8