Question

Question 10
Let y varies directly as x. if y = 12 when x = 4, then write a linear equation. What is the value of y when x = 5?

Answer 1

Given that, y varies directly as x.
i.e… $y\propto x\Rightarrow y=kx$ …(i) [where, k = arbitrary constant]
Given, y = 12 and x = 4 (substituting these values in Eq(i))
12 = 4k
$\Rightarrow k=\frac{12}{4}$
$\therefore$ k = 3.
On Putting the value of k in eq.(i) we get
y = 3x …(ii)
When x = 5, from Eq. (ii), we get,
y = 3 $\times$ 5 $\Rightarrow$ y = 15
Hence, the value of y is 15.