Question

if x varies directly as y, and x = 16 when y = 8, find x when y = 10.

Answer 1

Given that x varies direcrly ay. This can be repsened as below

$\begin{gathered} x\alpha y \\ x=Ky \end{gathered}$

When y=10 , x=16.

Substitute into formular to know their relationship

$\begin{gathered} x=Ky \\ 16=K\times8 \\ K=\frac{16}{8}=2,\text{then} \\ x=2y \end{gathered}$

To Find: find x when y = 10

$\begin{gathered} x=2y \\ y=10 \\ x=2\times10 \\ x=20 \end{gathered}$

Hence, when y =10, the value of x is 20