Question

Y is directly proportional to the square root of x

if y = 42 when x = 9 find,
x when y = 28​

Answer 1

Given:

y is directly proportional to the square root of x.

y = 42 when x = 9

To find:

x when y = 28​.

Solution:

We have,

y is directly proportional to the square root of x.

`y\propto √(x)`

`y=k√(x)` ...(i)

where, k is the constant of proportionality.

We have, y = 42 when x = 9.

`42=k√(9)`

`42=3k`

`(42)/(3)=k`

`14=k`

Putting k=14 in (i), we get

`y=14√(x)`

Putting y=28, we get

`28=14√(x)`

`(28)/(14)=√(x)`

`2=√(x)`

Taking square on both sides.

`2^2=x`

`4=x`

Therefore, the value of x is 4 when y=28.