Question

Y varies inversely as x. y = 18 when x = 5. Find y when x = 3.

Answer 1

If the variable

y

varies inversely as the variable

x

, then we can write this relationship as:

y

∝

1

x

Removing the proportionality sign and adding a proportionality constant, we have:

y

=

k

x

If the value of y is 18 when the value of x is 5, then:

18

=

k

5

k

=

18

×

5

=

90

Thus, the equation showing the relationship between the two variables is:

y

=

90

x

Using the above equation, the value of y when x = 3 is equal to:

y

=

90

3

=

30