Question

If z is directly proportional to the product of x and y and if z is 21 when x is 6 and y is 7, then x, y, and z are related by the equation z =

Answer 1

z =
`(1)/(2)` xy

Explanation:

given z is directly proportional to xy then the equation relating them is

z = kxy ← k is the constant of proportion

to find k use the condition z = 21 when x = 6 and y = 7

21 = k × 6 × 7 = 42k ( divide both sides by 42 )

`(21)/(42)` = k , that is

k =
`(1)/(2)`

equation relating them is

z =
`(1)/(2)` xy