Question

The first, second and third term of a proportion are
$\frac{1}{3},\frac{1}{6}\text{and}\frac{2}{5}\text{respectively}$.
What is the fourth term?

• A. $\frac{2}{5}$
• B. $\frac{1}{10}$
• C. $\frac{1}{5}$
• D. $\frac{1}{2}$

Answer 1

The correct option is C $\frac{1}{5}$

Let the fourth term be d.

$\text{So,}a:b::c:d=\frac{1}{3}:\frac{1}{6}::\frac{2}{5}:d$

We know that,
$d=\frac{b\times c}{a}$

$\Rightarrow d=\frac{\frac{1}{6}\times \frac{2}{5}}{\frac{1}{3}}$

$\Rightarrow d=\frac{1}{6}\times \frac{2}{5}\times 3$

$\Rightarrow d=\frac{1}{5}$