Question

To add $\frac{2}{5}$ and $\frac{3}{7}$ , first we have to find the LCM of ____________.

• A. 2 and 3
• B. 2 and 7
• C. 5 and 7
• D. 3 and 5

Answer 1

The correct option is C 5 and 7

To add two unlike fractions, first we have to find the LCM of the denominators of the given fractions and change them to like fractions by finding the equivalent fractions.

Here, $\frac{2}{5}+\frac{3}{7}$

LCM of $5$ and $7=35$

The equivalent fractions are

$\frac{2\times 7}{5\times 7}=\frac{14}{35}$

$\frac{3\times 5}{7\times 5}$ $=\frac{15}{35}$

$\therefore \frac{2}{5}+\frac{3}{7}$

$\Rightarrow \frac{14}{35}+\frac{15}{35}=\frac{29}{35}$