DAV Class 7 Maths Chapter 4 Worksheet 3

1. Which of the following statements are true?

a. (+34)3 x (-34)3 = (-34)6

\begin{align*} \left(+\frac{3}{4}\right)^3 \times \left(-\frac{3}{4}\right)^3 & = \left(-\frac{3}{4}\right)^6 \\ \end{align*}

Solution: False

Base is not the same.

b. (47)5 x (47)3 = (47)8

\begin{align*} \left(\frac{4}{7}\right)^5 \times \left(\frac{4}{7}\right)^3 = \left(\frac{4}{7}\right)^8 \\ \end{align*}

Solution : True

c. (-12)4 ÷ (-12)3 = (-12)

\begin{align*} \left(-\frac{1}{2}\right)^4 \div \left(-\frac{1}{2}\right)^3 = \left(-\frac{1}{2}\right) \end{align*}

Solution : True

d. (67)6 ÷ (67)0 = (67)0

\begin{align*} \left(\frac{6}{7}\right)^6 \div \left(\frac{6}{7}\right)^0 = \left(\frac{6}{7}\right)^0 \end{align*}

Solution : False

\begin{align*} \left(\frac{6}{7}\right)^6 \div \left(\frac{6}{7}\right)^0 = \left(\frac{6}{7}\right)^\boxed{6} \end{align*}

2. Fill in the blank in each of the following so as to make the statement true.

a. (-23) x (-23)3 = (-23)?

\begin{align*} \left(-\frac{2}{3}\right) \times \left(-\frac{2}{3}\right)^3 & = \left(-\frac{2}{3}\right)^\boxed{?} \end{align*}

Solution:

\begin{align*} & = \left(-\frac{2}{3}\right)^1 \times \left(-\frac{2}{3}\right)^3 \\ \\ & = \left(-\frac{2}{3}\right)^\boxed{1 + 3} \\ \\ & = \left(-\frac{2}{3}\right)^\boxed{4} \\ \\ \left(-\frac{2}{3}\right) \times \left(-\frac{2}{3}\right)^3 & = \left(-\frac{2}{3}\right)^\boxed{4} \end{align*}

b. (43)? ÷ (45)9 = (45)11

\begin{align*} \left(\frac{4}{5}\right)^\boxed{?} \times \left(\frac{4}{5}\right)^9 & = \left(\frac{4}{5}\right)^{11} \end{align*}

Solution:

\begin{align*} \left(\frac{4}{5}\right)^\boxed{?} & = \left(\frac{4}{5}\right)^{11} \div \left(\frac{4}{5}\right)^9 \\ \\ & = \left(\frac{4}{5}\right)^\boxed{11 - 9} \\ \\ & = \left(\frac{4}{5}\right)^2 \\ \\ \left(\frac{4}{5}\right)^\boxed{2} \times \left(\frac{4}{5}\right)^9 & = \left(\frac{4}{5}\right)^{11} \end{align*}

c. (-37)15 ÷ (-37)? = (-37)1

\begin{align*} \left(-\frac{3}{7}\right)^{15} \div \left(-\frac{3}{7}\right)^\boxed{?} & = \left(-\frac{3}{7}\right) \end{align*}

Solution:

\begin{align*} \left(-\frac{3}{7}\right)^\boxed{?} & = \left(-\frac{3}{7}\right)^{15} \div \left(-\frac{3}{7}\right)^1 \\ \\ & = \left(-\frac{3}{7}\right)^\boxed{15 - 1} \\ \\ & = \left(-\frac{3}{7}\right)^{14} \\ \\ \left(-\frac{3}{7}\right)^{15} \div \left(-\frac{3}{7}\right)^\boxed{14} & = \left(-\frac{3}{7}\right) \end{align*}

d. (-110)? ÷ (-110)8 = (-110)8

\begin{align*} \left(-\frac{1}{10}\right)^\boxed{?} \div \left(-\frac{1}{10}\right)^8 &= \left(-\frac{1}{10}\right)^8 \\ \end{align*}

Solution:

\begin{align*} \left(-\frac{1}{10}\right)^\boxed{?} &= \left(-\frac{1}{10}\right)^8 \times \left(-\frac{1}{10}\right)^8 \\ \\ &= \left(-\frac{1}{10}\right)^\boxed{8+8} \\ \\ &= \left(-\frac{1}{10}\right)^{16} \\ \\ \left(-\frac{1}{10}\right)^\boxed{16} \div \left(-\frac{1}{10}\right)^8 &= \left(-\frac{1}{10}\right)^8 \\ \end{align*}

e. (29)6 ÷ (29)0 = (29)?

\begin{align*} \left(\frac{2}{9}\right)^6 \div \left(\frac{2}{9}\right)^0 &= \left(\frac{2}{9}\right)^\boxed{?} \\ \end{align*}

Solution:

\begin{align*} \left(\frac{2}{9}\right)^\boxed{?} & = \left(\frac{2}{9}\right)^6 \div \left(\frac{2}{9}\right)^0 \\ \\ & = \left(\frac{2}{9}\right)^\boxed{6 - 0} \\ \\ & = \left(\frac{2}{9}\right)^\boxed{6} \\ \\ \left(\frac{2}{9}\right)^6 \div \left(\frac{2}{9}\right)^0 &= \left(\frac{2}{9}\right)^\boxed{6} \\ \end{align*}

f. (-1213)2 x (-1213)? = (-1213)5

\begin{align*} \left(-\frac{12}{13}\right)^2 \times \left(-\frac{12}{13}\right)^\boxed{?} &= \left(-\frac{12}{13}\right)^5 \\ \end{align*}

Solution:

\begin{align*} \left(-\frac{12}{13}\right)^2 \times \left(-\frac{12}{13}\right)^\boxed{?} &= \left(-\frac{12}{13}\right)^5 \\ \\ &= \left(-\frac{12}{13}\right)^5 \div \left(-\frac{12}{13}\right)^2 \\ \\ &= \left(-\frac{12}{13}\right)^\boxed{5 - 2} \\ \\ &= \left(-\frac{12}{13}\right)^\boxed{3} \\ \\ \left(-\frac{12}{13}\right)^2 \times \left(-\frac{12}{13}\right)^\boxed{3} &= \left(-\frac{12}{13}\right)^5 \\ \end{align*}

3. Simplify and express the result in exponential form.

a. (-37)3 x (-37)4

\begin{align*} \left(-\frac{3}{7}\right)^3 \times \left(-\frac{3}{7}\right)^4 \end{align*}

Solution:

\begin{align*} &= \left(-\frac{3}{7}\right)^{3 + 4} \\ \\ &= \left(-\frac{3}{7}\right)^7 \\ \end{align*}

b. (1112)15 x (1112)5 x (1112)10

\begin{align*} \left(\frac{11}{12}\right)^{15} \times \left(\frac{11}{12}\right)^5 \times \left(\frac{11}{12}\right)^{10} \end{align*}

Solution:

\begin{align*} &= \left(\frac{11}{12}\right)^{15 + 5 + 10} \\ &= \left(\frac{11}{12}\right)^{30} \end{align*}

c. (-911)9 ÷ (-911)7

\begin{align*} \left(-\frac{9}{11}\right)^9 \div \left(-\frac{9}{11}\right)^7 \end{align*}

Solution:

\begin{align*} &= \left(-\frac{9}{11}\right)^{9 - 7} \\ \\ &= \left(-\frac{9}{11}\right)^{2} \end{align*}

d. (14)8 ÷ (14)6

\begin{align*} \left(\frac{1}{4}\right)^8 \div \left(\frac{1}{4}\right)^6 \end{align*}

Solution:

\begin{align*} &= \left(\frac{1}{4}\right)^{8 - 6} \\ &= \left(\frac{1}{4}\right)^2 \end{align*}

4. Simplify and express the result as a rational number.

a. (57)4 ÷ (57)2

\begin{align*} \left(\frac{5}{7}\right)^4 \div \left(\frac{5}{7}\right)^2 \end{align*}

Solution:

\begin{align*} &= \left(\frac{5}{7}\right)^{4 - 2} \\ \\ &= \left(\frac{5}{7}\right)^2 \\ \\ &= \left(\frac{5}{7}\right) \times \left(\frac{5}{7}\right) \\ \\ &= \frac{25}{49} \end{align*}

b. (-23)2 x (-23)3

\begin{align*} \left(-\frac{2}{3}\right)^2 \times \left(-\frac{2}{3}\right)^3 \end{align*}

Solution:

\begin{align*} &= \left(-\frac{2}{3}\right)^{2+3} \\ \\ &= \left(-\frac{2}{3}\right)^5 \\ \\ &= \left(-\frac{2}{3}\right) \times \left(-\frac{2}{3}\right) \times \left(-\frac{2}{3}\right) \times \left(-\frac{2}{3}\right) \times \left(-\frac{2}{3}\right) \\ \\ &= -\frac{32}{243} \end{align*}

c. (34)3 x (34)2

\begin{align*} \left(\frac{3}{4}\right)^3 \times \left(\frac{3}{4}\right)^2 \end{align*}

Solution:

\begin{align*} &= \left(\frac{3}{4}\right)^{3+2} \\ \\ &= \left(\frac{3}{4}\right)^5 \\ \\ &= \left(\frac{3}{4}\right) \times \left(\frac{3}{4}\right) \times \left(\frac{3}{4}\right) \times \left(\frac{3}{4}\right) \times \left(\frac{3}{4}\right) \\ \\ &= \frac{243}{1024} \end{align*}

d. (-35)6 ÷ (-35)3

\begin{align*} \left(-\frac{3}{5}\right)^6 \div \left(-\frac{3}{5}\right)^3 \end{align*}

Solution:

\begin{align*} &= \left(-\frac{3}{5}\right)^{6-3} \\ \\ &= \left(-\frac{3}{5}\right)^3 \\ \\ &= \left(-\frac{3}{5}\right) \times \left(-\frac{3}{5}\right) \times \left(-\frac{3}{5}\right) \\ \\ &= -\frac{27}{125} \end{align*}

e. (-110)4 x (-110)2

\begin{align*} \left(-\frac{1}{10}\right)^4 \times \left(-\frac{1}{10}\right)^2 \end{align*}

Solution:

\begin{align*} &= \left(-\frac{1}{10}\right)^{4 + 2} \\ \\ &= \left(-\frac{1}{10}\right)^6 \\ \\ &= \left(-\frac{1}{10}\right) \times \left(-\frac{1}{10}\right) \times \left(-\frac{1}{10}\right) \times \left(-\frac{1}{10}\right) \times \left(-\frac{1}{10}\right) \times \left(-\frac{1}{10}\right) \\ \\ &= \frac{1}{1000000} \end{align*}

5. Evaluate

a. (34)3 x (23)2

\begin{align*} \left(\frac{3}{4}\right)^3 \times \left(\frac{2}{3}\right)^2 \end{align*}

Solution:

\begin{align*} &= \frac{3}{4} \times \frac{\cancel3}{\cancelto{2}4} \times \frac{\cancel{3}}{\cancelto{2}{4}} \times \frac{\cancelto{1}2}{\cancel{3}} \times \frac{\cancelto{1}2}{\cancel3} \\ \\ &= \frac{3}{4 \times 2 \times 2} \\ \\ &= \frac{3}{16} \end{align*}

b. [(13)6 ÷ (13)5] ÷ (13)

\begin{align*} \left[\left(\frac{1}{3}\right)^6 \div \left(\frac{1}{3}\right)^5\right] \div \left(\frac{1}{3}\right) \\ \end{align*}

Solution:

\begin{align*} &= \left[\left(\frac{1}{3}\right)^{6-5}\right] \div \left(\frac{1}{3}\right) \\ \\ &= \left(\frac{1}{3}\right)^{1} \div \left(\frac{1}{3}\right) \\ \\ &= \left(\frac{1}{3}\right)^{1-1} \\ \\ &= \left(\frac{1}{3}\right)^0 \\ \\ &= 1 \end{align*}

c. (24 x 25) ÷ 28

\begin{align*} ({2^4 \times 2^5}) \div {2^8} \\ \end{align*}

Solution:

\begin{align*} &= ({2^{4+5}}) \div {2^8} \\ \\ &= {2^{9}} \div {2^8} \\ \\ &= {2^{9-8}} \\ \\ &= 2^{1} \\ \\ &= 2 \end{align*}

d. (42 - 32) ÷ (17)2

\begin{align*} ({4^2 - 3^2}) \div {\left(\frac{1}{7}\right)^2} \\ \end{align*}

Solution:

\begin{align*} &= ({16 - 9}) \div {\left(\frac{1}{7}\right)} \times {\left(\frac{1}{7}\right)} \\ \\ &= {7} \div {\frac{1}{49}} \\ \\ &= 7 \times 49 \\ \\ &= 343 \end{align*}