S.chand publication New Learning Composite mathematics solution of class 7 Chapter 2 Fractions and Decimals Exercise 2E

 Exercise 2E

Question 1

Simplify:

(a) $\frac{4}{5}\div \frac{2}{5}$

$=\frac{4}{5}\times \frac{5}{2}$

=2

(b) $\frac{8}{19} \div \frac{3}{19}$

$=\frac{8}{19}\times \frac{19}{3}$

$=\frac{8}{3}=2\frac{2}{3}$

(c) $\frac{11}{20} \div \frac{7}{20}$

$=\frac{11}{20} \times \frac{20}{7}$

$=\frac{11}{7}=1\frac{4}{7}$

(d) $1\frac{1}{20}\div 3\frac{3}{20}$

Sol :

$=\frac{21}{20}\div \frac{63}{20}$

$=\frac{21}{20}\times \frac{20}{63}$

$=\frac{1}{3}$

Question 2

(a) $7\div \frac{1}{3}$

$=7\times \frac{3}{1}$

=21

(b) $1\div \frac{1}{10}$

$=1\times \frac{10}{1}$

=10

(c) $4\div 1\frac{1}{3}$

$=4 \div \frac{4}{3}$

$=4\times \frac{3}{4}$

=3

(d) $\frac{3}{8} \div 3$

$=\frac{3}{8}\times \frac{1}{3}$

$=\frac{1}{8}$

Question 3

(a) $1\frac{2}{5} \div 8\frac{3}{5}$

$=\frac{7}{5} \div \frac{43}{5}$

$=\frac{7}{5}\times \frac{5}{43}$

$=\frac{7}{43}$

(b) $7\frac{1}{2} \div 2\frac{7}{9}$

Sol :

$=\frac{15}{2} \div \frac{25}{9}$

$=\frac{15}{2} \times \frac{9}{25}$

$=\frac{27}{10}=2\frac{7}{10}$

(c) $4\frac{1}{6} \div 1\frac{1}{9}$

Sol :

$=\frac{25}{6} \div \frac{10}{9}$

$=\frac{25}{6} \times \frac{9}{10}$

$=\frac{15}{4}=3\frac{3}{4}$

Question 4

How many $2 \frac{2}{3}$ hour periods are there in 16 hours?

Sol :

$16 \div 2\frac{2}{3}$

$=16 \div \frac{8}{3}$

$=16\times \frac{3}{8}$

=6

9m 16hour $2\frac{2}{3}$ hour periods are 6 times 

Question 5

A $10 \frac{4}{5} \mathrm{~m}$ roll of plastic is cut into $\frac{3}{10} \mathrm{~cm}$ length. How many lengths are made?

Sol :

$10\frac{4}{5}$

$=\frac{54}{5}$

$=\frac{54\times 1000}{5}$

Lengths are made

∴$\frac{54\times 1000}{5} \div \frac{3}{10}$

$=\frac{54\times 1000}{5}\times \frac{10}{3}$