Question

If y is directly proportional to x2 and y=35 when x=1, find y if x=15. (Round off your answer to the nearest hundredth.)

Answer 1

y = 7875

Explanation:

given y is directly proportional to x² , then the equation relating them is

y = kx² ← k is the constant of proportionality

to find k use the condition y = 35 when x = 1 , then by substitution

35 = k × 1² , that is

k = 35

y = 35x² ← equation of proportionality

when x = 15 , then

y = 35 × 15² = 35 × 225 = 7875