# McGraw Hill Math Grade 8 Lesson 3.4 Answer Key Adding or Subtracting Fractions with Unlike Denominators

Practice the questions of McGraw Hill Math Grade 8 Answer Key PDF Lesson 3.4 Adding or Subtracting Fractions with Unlike Denominators to secure good marks & knowledge in the exams.

Question 1.
$$\frac{3}{4}$$ + $$\frac{2}{5}$$
$$\frac{23}{20}$$ or 1$$\frac{3}{20}$$,

Explanation:
Given to add $$\frac{3}{4}$$ + $$\frac{2}{5}$$ as
both don’t have common denominators first we multiply $$\frac{3}{4}$$ by 5 and $$\frac{2}{5}$$ by 4 we get
$$\frac{3 X 5}{4 X 5}$$ = $$\frac{15}{20}$$ and
$$\frac{2 X 4}{5 X 4}$$ = $$\frac{8}{20}$$
now we add numerators as $$\frac{15 + 8}{20}$$ = $$\frac{23}{20}$$ as numerator is greater than denominator we write in mixed fraction as $$\frac{1 X 20 + 3}{20}$$ = 1$$\frac{3}{20}$$.

Question 2.
$$\frac{5}{7}$$ + $$\frac{1}{3}$$
$$\frac{22}{21}$$ or 1$$\frac{1}{21}$$,

Explanation:
Given to add $$\frac{5}{7}$$ + $$\frac{1}{3}$$ as
both don’t have common denominators first we multiply $$\frac{5}{7}$$ by 3 and $$\frac{1}{3}$$ by 7 we get
$$\frac{5 X 3}{7 X 3}$$ = $$\frac{15}{21}$$ and
$$\frac{1 X 7}{3 X 7}$$ = $$\frac{7}{21}$$
now we add numerators as $$\frac{15 + 7}{21}$$ = $$\frac{22}{21}$$ as numerator is greater than denominator we write in mixed fraction as $$\frac{1 X 21 + 1}{21}$$ = 1$$\frac{1}{21}$$.

Question 3.
$$\frac{11}{20}$$ + $$\frac{2}{3}$$
$$\frac{73}{60}$$ or 1$$\frac{13}{60}$$,

Explanation:
Given to add $$\frac{11}{20}$$ + $$\frac{2}{3}$$ as
both don’t have common denominators first we multiply $$\frac{11}{20}$$ by 3 and $$\frac{2}{3}$$ by 20 we get
$$\frac{11 X 3}{20 X 3}$$ = $$\frac{33}{60}$$ and
$$\frac{2 X 20}{3 X 20}$$ = $$\frac{40}{60}$$
now we add numerators as $$\frac{33 + 40}{60}$$ = $$\frac{73}{60}$$ as numerator is greater than denominator we write in mixed fraction as $$\frac{1 X 60 + 13}{60}$$ = 1$$\frac{13}{60}$$.

Question 4.
$$\frac{1}{4}$$ – $$\frac{1}{13}$$
$$\frac{9}{52}$$,

Explanation:
Given to subtract $$\frac{1}{4}$$ – $$\frac{1}{13}$$ as
both don’t have common denominators first we multiply $$\frac{1}{4}$$ by 13 and $$\frac{1}{13}$$ by 4 we get
$$\frac{1 X 13}{4 X 13}$$ = $$\frac{13}{52}$$ and
$$\frac{1 X 4}{13 X 4}$$ = $$\frac{4}{52}$$
now we subtract numerators as $$\frac{13 – 4}{52}$$ = $$\frac{9}{52}$$.

Question 5.
$$\frac{1}{4}$$ – $$\frac{1}{9}$$
$$\frac{5}{36}$$,

Explanation:
Given to subtract $$\frac{1}{4}$$ – $$\frac{1}{9}$$ as
both don’t have common denominators first we multiply $$\frac{1}{4}$$ by 9 and $$\frac{1}{9}$$ by 4 we get
$$\frac{1 X 9}{4 X 9}$$ = $$\frac{9}{36}$$ and
$$\frac{1 X 4}{9 X 4}$$ = $$\frac{4}{36}$$
now we subtract numerators as $$\frac{9 – 4}{36}$$ = $$\frac{5}{36}$$.

Question 6.
$$\frac{2}{21}$$ + $$\frac{1}{3}$$
$$\frac{27}{63}$$ or $$\frac{9}{21}$$ or
$$\frac{3}{7}$$,

Explanation:
Given to add $$\frac{2}{21}$$ + $$\frac{1}{3}$$ as
both don’t have common denominators first we multiply $$\frac{2}{21}$$ by 3 and $$\frac{1}{3}$$ by 21 we get
$$\frac{2 X 3}{21 X 3}$$ = $$\frac{6}{63}$$ and
$$\frac{1 X 21}{3 X 21}$$ = $$\frac{21}{63}$$
now we add numerators as $$\frac{6 + 21}{63}$$ = $$\frac{27}{63}$$ further can be divided by 3 we get $$\frac{9}{21}$$ again further can be divided by 3 we get $$\frac{3}{7}$$.

Question 7.
$$\frac{34}{11}$$ – $$\frac{1}{3}$$
$$\frac{91}{33}$$ or 2$$\frac{25}{33}$$,

Explanation:
Given to subtract $$\frac{34}{11}$$ – $$\frac{1}{3}$$ as
both don’t have common denominators first we multiply $$\frac{34}{11}$$ by 3 and $$\frac{1}{3}$$ by 11 we get
$$\frac{34 X 3}{11 X 3}$$ = $$\frac{102}{33}$$ and
$$\frac{1 X 11}{3 X 11}$$ = $$\frac{11}{33}$$
now we subtract numerators as $$\frac{102 – 11}{33}$$ = $$\frac{91}{33}$$ as numerator is greater than denominator we write in mixed fraction as $$\frac{2 X 33 + 25}{33}$$ = 2$$\frac{25}{33}$$.

Question 8.
$$\frac{11}{7}$$ + $$\frac{1}{6}$$
$$\frac{73}{42}$$ or 1$$\frac{31}{42}$$,

Explanation:
Given to add $$\frac{11}{7}$$ + $$\frac{1}{6}$$ as
both don’t have common denominators first we multiply $$\frac{11}{7}$$ by 6 and $$\frac{1}{6}$$ by 7 we get
$$\frac{11 X 6}{7 X 6}$$ = $$\frac{66}{42}$$ and
$$\frac{1 X 7}{6 X 7}$$ = $$\frac{7}{42}$$
now we add numerators as $$\frac{66 + 7}{42}$$ = $$\frac{73}{42}$$ as numerator is greater than denominator we write in mixed fraction as $$\frac{1 X 42 + 31}{42}$$ = 1$$\frac{31}{42}$$.

Question 9.
$$\frac{11}{15}$$ – $$\frac{2}{3}$$
$$\frac{3}{45}$$ or $$\frac{1}{15}$$,

Explanation:
Given to subtract $$\frac{11}{15}$$ – $$\frac{2}{3}$$ as
both don’t have common denominators first we multiply $$\frac{11}{15}$$ by 3 and $$\frac{2}{3}$$ by 15 we get
$$\frac{11 X 3}{15 X 3}$$ = $$\frac{33}{45}$$ and
$$\frac{2 X 15}{3 X 15}$$ = $$\frac{30}{45}$$
now we subtract numerators as $$\frac{33 – 30}{45}$$ = $$\frac{3}{45}$$ further can be divided by 3 we get $$\frac{1}{15}$$.

Question 10.
$$\frac{5}{8}$$ – $$\frac{2}{7}$$
$$\frac{19}{56}$$,

Explanation:
Given to subtract $$\frac{5}{8}$$ – $$\frac{2}{7}$$ as
both don’t have common denominators first we multiply $$\frac{5}{8}$$ by 7 and $$\frac{2}{7}$$ by 8 we get
$$\frac{5 X 7}{8 X 7}$$ = $$\frac{35}{56}$$ and
$$\frac{2 X 8}{7 X 8}$$ = $$\frac{16}{56}$$
now we subtract numerators as $$\frac{35 – 16}{56}$$ = $$\frac{19}{56}$$.

Question 11.
$$\frac{14}{11}$$ + $$\frac{3}{7}$$
$$\frac{131}{77}$$ or 1$$\frac{54}{77}$$,

Explanation:
Given to add $$\frac{14}{11}$$ + $$\frac{3}{7}$$ as
both don’t have common denominators first we multiply $$\frac{14}{11}$$ by 7 and $$\frac{3}{7}$$ by 11 we get
$$\frac{14 X 7}{11 X 7}$$ = $$\frac{98}{77}$$ and
$$\frac{3 X 11}{7 X 11}$$ = $$\frac{33}{77}$$
now we add numerators as $$\frac{98 + 33}{77}$$ = $$\frac{131}{77}$$ as numerator is greater than denominator we write in mixed fraction as $$\frac{1 X 77 + 54}{77}$$ = 1$$\frac{54}{77}$$.

Question 12.
$$\frac{11}{12}$$ – $$\frac{3}{5}$$
$$\frac{47}{60}$$,

Explanation:
Given to subtract $$\frac{11}{12}$$ – $$\frac{3}{15}$$ as
both don’t have common denominators first we multiply $$\frac{11}{12}$$ by 15 and $$\frac{3}{15}$$ by 12 we get
$$\frac{11 X 15}{12 X 15}$$ = $$\frac{165}{180}$$ and
$$\frac{2 X 12}{15 X 12}$$ = $$\frac{24}{180}$$
now we subtract numerators as $$\frac{165 – 24}{180}$$ = $$\frac{141}{180}$$ further can be divided by 3 we get $$\frac{47}{60}$$.