Question

y is inversely proportional to x.
Given that y = 9, when x=8, find y when x = 6.

Answer 1

Step-by-step explanation:

y

is inversely proportional to

x

, and if

y

=

6

when

x

=

4

then

y

=

24

x

−−−−−−− .

Using this formula we find that if

y

=

8

then

x

=

3

−−−−−

Explanation:

Given,

y

is inversely proportional to

x

or

y

∝

x

−

1

this is if and only if

y

∝

1

x

⇔

y

=

1

x

k

Also, we know that if

y

=

6

when

x

=

4

then

6

=

1

4

k

⇔

multiply both sides by

4

24

=

k

this is our constant of proportionality

⇒

this gives us our formula

y

=

24

x

Then consider when

y

=

8

then

8

=

24

x

⇔

multiply both sides by

x

8

x

=

24

⇔

divide both sides by

8

x

=

3

Answer 2

Step-by-step explanation:

x = 8

y = 9

.'. y = a ÷ x

.'. 9 = a ÷ 8

.'. a = 9×8

.'. a = 72

.'. y = 72 / 6

.'. y = 12