Question

y is directly proportional to x. If y = 6 when x = 2. Find the constant of proportionality, the value of y when x = 7, the value of y when x = 9, the value of x when y = 9, the value of x when y = 30

Answer 1

see explanation

Explanation:

given that y is directly proportional to x , then the equation relating them is

y = kx ← k is the constant of proportionality

to find k , use the condition y = 6 when x = 2

6 = 2k ( divide both sides by 2 )

3 = k

y = 3x ← equation of proportion

when x = 7 , then

y = 3 × 7 = 21

when x = 9 , then

y = 3 × 9 = 27

when y = 9 , then

9 = 3x ( divide both sides by 3 )

3 = x

when y = 30 , then

30 = 3x ( divide both sides by 3 )

10 = x