Question

Y

is inversely proportional to
x
.
When
y
=
25
,
x
=
4

Work out
x
when
y
=
20

Answer 1

x = 5

Explanation:

Given that y is inversely proportional to x then the equation relating them is

y =
`(k)/(x)` ← k is the constant of proportion

To find k use the condition when y = 25 , x = 4 , then

25 =
`(k)/(4)` ( multiply both sides by 4 )

100 = k

y =
`(100)/(x)` ← equation of proportion

When y = 20, then

20 =
`(100)/(x)` ( multiply both sides by x )

20x = 100 ( divide both sides by 20 )

x = 5