Question

If y= 1/5 when x=3, find y when x=4, given that y varies directly with x

Answer 1

`y = (4)/(15)`

Explanation:

To find y when x=4, we must first find the relationship between them

The statement

y varies directly with x is written as

`y \: \: \: \alpha \: \: \: kx`

where k is the constant of proportionality

From the question

when y = 1/5

x = 3

Substitute the values into the above formula and solve

That's

`(1)/(5) = 3k \\ 15k = 1 \\ k = (1)/(15)`

So the formula for the variation is

`y = (x)/(15)`

From the question

when x = 4

`y = (4)/(15)`

Hope this helps you