Question

Find the difference:
$\frac{13}{35}-\frac{5}{21}$

• A. $\frac{2}{15}$
• B. $\frac{4}{15}$
• C. $\frac{13}{105}$
• D. $\frac{17}{105}$

Answer 1

The correct option is A

$\frac{2}{15}$

To find the value of $\frac{13}{35}-\frac{5}{21}$, first we need to find the LCM of 35 and 21,
$\begin{array}{cc}3& 35,21\\ 7& 35,7\\ & 5,1\end{array}$

LCM of 35 and 21 $=3\times 7\times 5=105$

$\frac{13}{35}-\frac{5}{21}$ $=\frac{13\times 3}{35\times 3}-\frac{5\times 5}{21\times 5}=\frac{39-25}{105}=\frac{14}{105}=\frac{7\times 2}{7\times 15}\text{[Cancelling 7]}=\frac{2}{15}$