Question

If y is 5 when x is 2.5 and y varies directly with x, find y when x is 10

Answer 1

Answer:

If x varies directly as y, then x=ky. y=5 and x=2.5 are substituted into x=ky to find k.

2.5=5k

k=2.5/5

k=5.

K =5 is substituted in x=ky to find y where x is 10.

x=5y

10=5y

y=10/2

y=2

Answer 2

Answer:  The required value of y is 20.

Step-by-step explanation:  Given that y is 5 when x is 2.5 and y varies directly with x.

We are to find the value of y when x is 10.

According to the given information, we can write

$y\propto x\\\\\Rightarrow y=kx~~~~~~~~~~[\textup{where k is the constant of proportionality}]$

When y = 5 and x = 2.5, then we have

$5=k\times2.5\\\\\Rightarrow k=\dfrac{5}{2.5}\\\\\Rightarrow k=2.$

So, we get

$y=2x.$

Therefore, when x = 10, then the value of y is

$y=2\times10=20.$

Thus, the required value of y is 20.