Question

If y is directly proportional to x and y = 5 when x = 2, find the value of y when
x=7.​

Answer 1

Answer:

y = 17.5

Step-by-step explanation:

y is directly proportional to x means that

y = k.x

when y=5, x=2 --> k = y/x = 5/2

when x=7

y = k.x = 5/2 . 7 = 35/2 = 17.5

Answer 2

Answer:

y = 17.5

Step-by-step explanation:

Given y is directly proportional to x then the equation relating them is

y = kx ← k is the constant of proportion

To find k use the condition y = 5 when x = 2, thus

5 = 2k ( divide both sides by 2 )

2.5 = k

y = 2.5x ← equation of proportion

When x = 7, then

y = 2.5 × 7 = 17.5