Ans: (b) Explanation: When multiplying expressions with the same base, we add the exponents: \(x^{\frac{2}{3}} \cdot x^{\frac{1}{3}} = x^{\frac{2}{3} + \frac{1}{3}} = x^{\frac{3}{3}} = x^1 = x\). Option (a) incorrectly multiplies the exponents, option (c) incorrectly subtracts them, and option (d) incorrectly adds them as whole numbers.
Q2: Which of the following is equivalent to \(\sqrt[4]{16x^8}\)? (a) \(4x^2\) (b) \(2x^2\) (c) \(2x^4\) (d) \(4x^4\)
Solution:
Ans: (b) Explanation: We can rewrite the radical using rational exponents: \(\sqrt[4]{16x^8} = (16x^8)^{\frac{1}{4}} = 16^{\frac{1}{4}} \cdot x^{8 \cdot \frac{1}{4}} = 2 \cdot x^2 = 2x^2\). Since \(16 = 2^4\), we have \(16^{\frac{1}{4}} = 2\). Option (a) uses an incorrect value for \(16^{\frac{1}{4}}\), while options (c) and (d) incorrectly simplify the exponent on \(x\).
Ans: (b) Explanation: The expression \(27^{\frac{2}{3}}\) means we take the cube root of 27 and then square it: \(27^{\frac{2}{3}} = (27^{\frac{1}{3}})^2 = 3^2 = 9\). Alternatively, \(27^{\frac{2}{3}} = (\sqrt[3]{27})^2 = 3^2 = 9\). Option (a) incorrectly multiplies 3 by 2, option (c) incorrectly multiplies 9 by 2, and option (d) only completes the first step.
Ans: (b) Explanation: When dividing expressions with the same base, we subtract the exponents: \(\frac{x^{\frac{5}{6}}}{x^{\frac{1}{6}}} = x^{\frac{5}{6} - \frac{1}{6}} = x^{\frac{4}{6}} = x^{\frac{2}{3}}\). Option (c) is correct before simplifying the fraction, but option (b) is the simplified form. Option (a) incorrectly multiplies the exponents, and option (d) incorrectly performs the subtraction.
Q5: Which expression is equivalent to \(\sqrt[3]{x^6y^9}\)? (a) \(x^3y^6\) (b) \(x^2y^3\) (c) \(x^2y^6\) (d) \(x^3y^3\)
Solution:
Ans: (b) Explanation: Converting to rational exponents: \(\sqrt[3]{x^6y^9} = (x^6y^9)^{\frac{1}{3}} = x^{6 \cdot \frac{1}{3}} \cdot y^{9 \cdot \frac{1}{3}} = x^2y^3\). Each exponent is multiplied by \(\frac{1}{3}\). Option (a) incorrectly divides by 2, option (c) only simplifies \(x\) correctly, and option (d) only simplifies \(y\) correctly.
Ans: (b) Explanation: Apply the power of a product rule: \((8x^6)^{\frac{1}{3}} = 8^{\frac{1}{3}} \cdot (x^6)^{\frac{1}{3}} = 2 \cdot x^{6 \cdot \frac{1}{3}} = 2 \cdot x^2 = 2x^2\). Since \(8 = 2^3\), we have \(8^{\frac{1}{3}} = 2\). Option (a) incorrectly computes the exponent on \(x\), option (c) doesn't simplify 8, and option (d) uses incorrect values for both parts.
Q7: What is the value of \(16^{-\frac{3}{4}}\)? (a) \(\frac{1}{8}\) (b) \(-12\) (c) \(\frac{1}{12}\) (d) \(8\)
Solution:
Ans: (a) Explanation: A negative exponent means we take the reciprocal: \(16^{-\frac{3}{4}} = \frac{1}{16^{\frac{3}{4}}}\). Now, \(16^{\frac{3}{4}} = (16^{\frac{1}{4}})^3 = 2^3 = 8\), so \(16^{-\frac{3}{4}} = \frac{1}{8}\). Option (b) incorrectly treats the negative exponent as multiplication, option (c) uses an incorrect value, and option (d) forgets the negative sign.
Ans: (a) Explanation: Convert radicals to rational exponents: \(\sqrt{x} = x^{\frac{1}{2}}\) and \(\sqrt[4]{x} = x^{\frac{1}{4}}\). Then multiply: \(x^{\frac{1}{2}} \cdot x^{\frac{1}{4}} = x^{\frac{1}{2} + \frac{1}{4}} = x^{\frac{2}{4} + \frac{1}{4}} = x^{\frac{3}{4}}\). Option (b) incorrectly subtracts the exponents, option (c) incorrectly adds as whole numbers, and option (d) uses an incorrect common denominator.
Section B: Fill in the Blanks
Q9: The expression \(a^{\frac{m}{n}}\) is equivalent to \(\sqrt[n]{a^m}\) or __________.
Solution:
Ans: \((\sqrt[n]{a})^m\) Explanation: A rational exponent \(\frac{m}{n}\) can be interpreted as taking the \(n\)th root and then raising to the \(m\)th power, or vice versa. Both \(\sqrt[n]{a^m}\) and \((\sqrt[n]{a})^m\) are equivalent forms.
Q10: When simplifying \(x^{\frac{2}{5}} \cdot x^{\frac{3}{5}}\), you __________ the exponents to get \(x^1\).
Solution:
Ans: add Explanation: The product rule for exponents states that when multiplying powers with the same base, you add the exponents: \(x^a \cdot x^b = x^{a+b}\).
Q11: The simplified form of \(32^{\frac{1}{5}}\) is __________.
Solution:
Ans: 2 Explanation: The expression \(32^{\frac{1}{5}}\) means the fifth root of 32. Since \(32 = 2^5\), we have \(32^{\frac{1}{5}} = (2^5)^{\frac{1}{5}} = 2^{5 \cdot \frac{1}{5}} = 2^1 = 2\).
Q12: An exponent of \(-\frac{1}{2}\) on a base \(a\) is equivalent to __________ divided by \(\sqrt{a}\), assuming \(a > 0\).
Solution:
Ans: 1 Explanation: A negative rational exponent indicates a reciprocal: \(a^{-\frac{1}{2}} = \frac{1}{a^{\frac{1}{2}}} = \frac{1}{\sqrt{a}}\). This represents 1 divided by the square root of \(a\).
Q13: The expression \(\sqrt[5]{x^{10}}\) simplifies to __________.
Solution:
Ans: \(x^2\) Explanation: Converting to rational exponents: \(\sqrt[5]{x^{10}} = x^{\frac{10}{5}} = x^2\). The exponent \(\frac{10}{5}\) simplifies to 2.
Q14: When dividing \(a^{\frac{7}{3}}\) by \(a^{\frac{1}{3}}\), you __________ the exponents.
Solution:
Ans: subtract Explanation: The quotient rule for exponents states that when dividing powers with the same base, you subtract the exponents: \(\frac{a^m}{a^n} = a^{m-n}\).
Section C: Word Problems
Q15: The radius of a sphere is given by the formula \(r = \left(\frac{3V}{4\pi}\right)^{\frac{1}{3}}\), where \(V\) is the volume. Find the radius of a sphere with volume \(36\pi\) cubic centimeters. Express your answer in simplified form.
Solution:
Ans: Substitute \(V = 36\pi\) into the formula: \[r = \left(\frac{3(36\pi)}{4\pi}\right)^{\frac{1}{3}}\] Simplify inside the parentheses: \[r = \left(\frac{108\pi}{4\pi}\right)^{\frac{1}{3}} = (27)^{\frac{1}{3}}\] Find the cube root: \[r = \sqrt[3]{27} = 3\] Final Answer: 3 centimeters
Q16: The intensity of light \(I\) at a distance \(d\) from a source follows the relationship \(I = k \cdot d^{-2}\), where \(k\) is a constant. If the intensity at 4 meters is 25 watts per square meter, find the constant \(k\).
Solution:
Ans: Substitute \(I = 25\) and \(d = 4\) into the equation: \[25 = k \cdot 4^{-2}\] Simplify \(4^{-2}\): \[4^{-2} = \frac{1}{4^2} = \frac{1}{16}\] So the equation becomes: \[25 = k \cdot \frac{1}{16}\] Multiply both sides by 16: \[k = 25 \times 16 = 400\] Final Answer: 400 watts·meters²
Q17: A company's profit \(P\) (in thousands of dollars) after \(t\) years is modeled by \(P = 50t^{\frac{3}{2}}\). How much profit does the company make after 4 years?
Solution:
Ans: Substitute \(t = 4\) into the formula: \[P = 50(4)^{\frac{3}{2}}\] Calculate \(4^{\frac{3}{2}}\): \[4^{\frac{3}{2}} = (4^{\frac{1}{2}})^3 = 2^3 = 8\] Multiply: \[P = 50 \times 8 = 400\] Final Answer: 400 thousand dollars or $400,000
Q18: The surface area \(S\) of a cube is related to its volume \(V\) by the formula \(S = 6V^{\frac{2}{3}}\). Find the surface area of a cube with volume 64 cubic inches.
Q19: The relationship between the period \(T\) of a pendulum (in seconds) and its length \(L\) (in meters) is given by \(T = 2\pi L^{\frac{1}{2}}\). If a pendulum has a period of \(4\pi\) seconds, find its length.
Solution:
Ans: Substitute \(T = 4\pi\) into the formula: \[4\pi = 2\pi L^{\frac{1}{2}}\] Divide both sides by \(2\pi\): \[2 = L^{\frac{1}{2}}\] Square both sides to solve for \(L\): \[L = 2^2 = 4\] Final Answer: 4 meters
Q20: The mass \(m\) of a radioactive substance after \(t\) hours is given by \(m = 100 \cdot 2^{-\frac{t}{3}}\) grams. Find the mass of the substance after 9 hours.
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