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Surds & Indices Questions and Answers

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51.

The value of \((\frac{32}{243})^{-\frac{4}{5}}\) is:

Answer: D

\((\frac{32}{243})^{-\frac{4}{5}} \)

\(= (\frac{243}{32})^{\frac{4}{5}} \)

\(= [(\frac{3}{2})^5]^{\frac{4}{5}} \)

\(= \frac{81}{16}\)

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52.

\((\frac{1}{216})^{-\frac{2}{3}}\div(\frac{1}{27})^{-\frac{4}{3}}=?\)

Answer: C

\((\frac{1}{216})^{-\frac{2}{3}}\div(\frac{1}{27})^{-\frac{4}{3}} \)

\(= 216^{\frac{2}{3}}\div27^{\frac{4}{3}} \)

\(= (63)^{\frac{2}{3}}\div(33)^{\frac{4}{3}} \)

\(= \frac{4}{9}\)

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53.

\[ \frac{2^{n+4} - 2 \cdot 2^{n}}{2 \cdot 2^{n+3}} + 2^{-3} \ \text{ is equal to:} \]

Answer: D

Factor \( 2^{n} \) out of the fraction.

\[ \frac{2^{n+4} - 2 \cdot 2^{n}}{2 \cdot 2^{n+3}} = \frac{2^{n}(16 - 2)}{2^{n}(16)} = \frac{14}{16} = \frac{7}{8} \]

\[ \frac{7}{8} + 2^{-3} = \frac{7}{8} + \frac{1}{8} = 1 \]

The \( 2^{n} \) cancels entirely, so the answer does not depend on \( n \).

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54.

If \(5\sqrt{5}\times5^3\div5^{-\frac{3}{2}}=5^{a+2}\), the value of \(a\) is:

Answer: A

\(5^{\frac{3}{2}}\times5^3\div5^{3\frac{3}{2}}=5^{a+2} \)

\(\Rightarrow 5^{\frac{3}{2}}+3+\frac{3}{2}=5^{a+2} \)

\(\Rightarrow \frac{3}{2}+3+\frac{3}{2}=a+2 \)

\(\Rightarrow a+2=6 \)

\(\therefore a=4\)

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55.

If \(\sqrt{2n}=64\), then the value of \(n\) is:

Answer: D

\(\sqrt{2n}=64 \)

\(\Rightarrow 2^{\frac{n}{2}}=64=2^6 \)

\(\Rightarrow \frac{n}{2}=6 \)

\(\therefore n=12\)

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56.

The simplified form of \((x^{\frac{7}{2}}\div x^{\frac{5}{2}})\times \sqrt{y3}\div \sqrt{y}\) is:

Answer: D

\((x^{\frac{7}{2}}\div x^{\frac{5}{2}})\times \sqrt{y3}\div \sqrt{y} \)

\(= x^{(\frac{7}{2}-\frac{5}{2})}\times y^{(\frac{3}{2}-\frac{1}{2})} \)

\(= xy\)

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57.

If \(m\) and \(n\) are whole numbers such that \(m^n = 169\), then the value of \((m-1)^{n+1}\) is:

Answer: D

\( 169 = 13^{2} \), so \( m = 13 \) and \( n = 2 \).

\[ (m-1)^{n+1} = 12^{3} = 1728 \]

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58.

The simplified form of \(\frac{x^{\frac{9}{2}}\times \sqrt{y^5}}{x^{\frac{7}{2}}\times \sqrt{y^3}}\) is:

Answer: B

Exp: \(\frac{x^{\frac{9}{2}}\times \sqrt{y^5}}{x^{\frac{7}{2}}\times \sqrt{y^3}}\)  is:

 \(= x^{\frac{9}{2}-\frac{5}{2}}\times y^{\frac{7}{2}-\frac{3}{2}} \)

\(= x^2 . y^2\)

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59.

If \(\sqrt{(3+3\sqrt{x})} = 2\), then \(x\) is equal to:

Answer: A

Exp: On squaring both sides, we get:

\(3+3\sqrt{x} = 4\) or \(3\sqrt{x} = 1\)

Cubing both sides, we get \(x = (1\times 1\times 1) = 1\)

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60.

If \(x\) is an integer, find the minimum value of \(x\) such that \(0.00001154111\times 10^x\) exceeds 1000.

Answer: A

Exp: Considering from the left if the decimal point is shifted by 8 places to the right, the number

becomes 1154.111. Therefore, \(0.00001154111\times 10^x\) exceeds 1000 when \(x\) has a minimum value of 8.

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