A varies jointly as b and c. Find a when b = 7 and c = 9, if the constant of the variation is 3.

A joint variation is a direct variation with two or more variables. A varies jointly as b and c is equivalent to a = kbc, where k is a non-zero constant variation that is also known as the constant of proportionality.

a varies jointly as b and c

⇒ a = k × b × c --- eq(1)

To find a when b = 7 and c = 9.

Substitute k = 3, b = 7 and c = 9 in the equation of variation

a = 3 × 7 × 9

a = 189

A varies jointly as b and c. Find a when b = 7 and c = 9, if the constant of the variation is 3.

Summary:

If a varies jointly as b and c, the value of a will be 189, when b = 7 and c = 9 and the constant is the variation is 3.