Question

If y is 2.5 when x is 5 and i varies directly with x, find y when x is 14 ?

Answer 1

The correct answer is, y = 7

Explanation:

It is given that,If y is 2.5 when x is 5 and i varies directly with x

To find the relationship between x and y

From the given data, we can write,

x = 5 the y = 2.5

2.5 = 5/2

Therefore y = x/2

To find the value of y

x = 14

y = x/2 = 14/2 = 7

Therefore the correct answer is, y = 7

Answer 2

`y = 7`

EXPLANATION

If y varies directly with x, we write the mathematical statement;

`y \propto \: x`

When we introduce the constant of proportionality k, then we write the equation,

`y = kx`

If y is 2.5 when x is 5,then we have;

`2.5 = 5k`

`k = (2.5)/(5)`

`k = 0.5`

The equation of variation then becomes;

`y = 0.5x`

when x=14,

`y = 0.5(14)`

`y = 7`