S.chand publication New Learning Composite mathematics solution of class 8 Chapter 1 Rational numbers Exercise 1B

 Exercise 1B

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Q1  | Ex-1B |Class 8 |Rational Numbers | S.Chand | New Learning | Composite mathematics | myhelper

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Question 1

Find the sum or difference. Simplify if possible.

(a) $\frac{7}{20}+\frac{11}{20}$

Sol :

$=\frac{7+11}{20}=\frac{18}{20}=\frac{9}{10}$

(b) $\frac{1}{12}+\frac{7}{12}$

Sol :

$=\frac{1+7}{12}=\frac{8}{12}=\frac{1}{1}$

(c) $\frac{3}{10}-\frac{7}{10}$

Sol :

$=\frac{3-7}{10}=-\frac{4}{10}=-\frac{2}{5}$

(d) $-\frac{37}{7}-\frac{24}{7}$

Sol :

$=-\frac{37}{7}-\frac{24}{7}=\frac{-61}{7}$

(e) $\frac{112}{13}+\frac{-229}{13}$

Sol :

$=\frac{112-229}{13}=\frac{-117}{13}$

=-9

(f) $\frac{-243}{58}+\frac{719}{58}+\frac{273}{-58}$

Sol :

$=\fracc{-243}{58}+\frac{719}{58}+\frac{-273}{58}$

$=\frac{-243+719-273}{58}$

$=\frac{203}{58}$

(g) $\frac{-44}{5}-\frac{3}{5}$

Sol :

$=\frac{-44}{5}-\frac{3}{5}=\frac{-44-3}{5}=\frac{-47}{5}$

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Q2  | Ex-1B |Class 8 |Rational Numbers | S.Chand | New Learning | Composite mathematics | myhelper

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Question 2

(a) $\frac{5}{7}-\frac{3}{8}$

Sol :

$=\frac{40-21}{56}=\frac{19}{56}$

(b) $\frac{7}{18}-\frac{5}{6}$

Sol :

$=\frac{7-15}{18}=\frac{-8}{18}=\frac{-4}{9}$

(c) $\frac{3}{8}-\frac{5}{32}$

Sol :

$=\frac{12-5}{32}=\frac{7}{32}$

(d) $\frac{7}{-9}+\frac{1}{-6}$

Sol :

$=\frac{-42-9}{54}=\frac{-51}{54}=\frac{-17}{18}$

(e) $\frac{29}{5}+\left(\frac{-23}{7}\right)$

Sol :

$=\frac{29}{5}-\frac{23}{7}=\frac{203-115}{35}$ 

$=\frac{88}{35}=2\frac{18}{35}$

(f) 9 –$\frac{81}{7}$

Sol :

$=\frac{63-81}{7}=\frac{-18}{7}=-2\frac{4}{7}$

(g) $\frac{-92}{11}-(-9)$

Sol :

$=-\frac{92}{11}+9=\frac{-92+99}{11}=\frac{7}{11}$

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Q3  | Ex-1B |Class 8 |Rational Numbers | S.Chand | New Learning | Composite mathematics | myhelper

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Question 3

Simplify

$\frac{3}{4}-\frac{5}{7}+\frac{9}{14}$

Sol :

$=\frac{3}{4}-\left(\frac{10-9}{14}\right)$

$=\frac{3}{4}-\frac{10}{14}$

$=\frac{21-2}{28}=\frac{19}{28}$

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Q4  | Ex-1B |Class 8 |Rational Numbers | S.Chand | New Learning | Composite mathematics | myhelper

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Question 4

$5\frac{7}{9}-1\frac{1}{10}-7\frac{11}{15}$

Sol :

$=\frac{52}{9}-\frac{11}{10}-\frac{116}{15}$

LCM of  9, 10 , 15 is 90

$=\frac{52\times -11\times 9-116\times 6}{90}$

$=\frac{520-99-696}{90}=\frac{520-795}{90}=\frac{-275}{90}$

$=-3\frac{5}{90}$