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Quantitative Aptitude

SQUARE ROOT AND CUBE ROOT MCQs

Square Roots, Cube Roots, Squares And Square Roots

Total Questions : 547 | Page 48 of 55 pages
Question 471. Value of $$\sqrt {0.01} \times \root 3 \of {0.008} - 0.02$$     is = ?
  1.    0
  2.    1
  3.    2
  4.    3
 Discuss Question
Answer: Option A. -> 0
$$\eqalign{
& = \sqrt {0.01} \times \root 3 \of {0.008} - 0.02{\text{ }} \cr
& = \sqrt {{{\left( {0.1} \right)}^2}} \times \root 3 \of {{{\left( {0.2} \right)}^3}} - 0.02 \cr
& = 0.1 \times 0.2 - 0.02 \cr
& = 0.02 - 0.02 \cr
& = 0 \cr} $$
Question 472. $$\root 3 \of {\sqrt {0.000064} } = ?$$
  1.    0.02
  2.    0.2
  3.    2
  4.    None of these
 Discuss Question
Answer: Option B. -> 0.2
$$\eqalign{
& = \sqrt {0.000064} \cr
& = \sqrt {\frac{{64}}{{{{10}^6}}}} \cr
& = \frac{8}{{{{10}^3}}} \cr
& = \frac{8}{{1000}} \cr
& = 0.008 \cr
& \therefore \root 3 \of {\sqrt {0.000064} } \cr
& = \root 3 \of {0.008} \cr
& = \root 3 \of {\frac{8}{{1000}}} \cr
& = \frac{2}{{10}} \cr
& = 0.2 \cr} $$
Question 473. The value of $${\text{ }}\root 3 \of {\frac{{0.2 \times 0.2 \times 0.2 + 0.04 \times 0.04 \times 0.04}}{{0.4 \times 0.4 \times 0.4 + 0.08 \times 0.08 \times 0.08}}} $$        is ?
  1.    0.125
  2.    0.25
  3.    0.5
  4.    0.75
 Discuss Question
Answer: Option C. -> 0.5
$$\eqalign{
& = \root 3 \of {\frac{{0.2 \times 0.2 \times 0.2 + 0.04 \times 0.04 \times 0.04}}{{0.4 \times 0.4 \times 0.4 + 0.08 \times 0.08 \times 0.08}}} \cr
& = \root 3 \of {\frac{{0.008 + 0.000064}}{{0.064 + 0.000512}}} \cr
& = \root 3 \of {\frac{{0.008064}}{{0.064512}}} \cr
& = \root 3 \of {\frac{{8064}}{{64512}}} \cr
& = \root 3 \of {\frac{1}{8}} \cr
& = \frac{1}{2} \cr
& = 0.5 \cr} $$
Question 474. What is the smallest number by which 3600 be divided to make it a perfect cube ?
  1.    9
  2.    50
  3.    300
  4.    450
 Discuss Question
Answer: Option D. -> 450
$$3600 = {2^3} \times {5^2} \times {3^2} \times 2$$
To make it a perfect cube, it must be divided by   $${5^2} \times {3^2} \times 2,i.e.,450$$
Question 475. If $$\sqrt {1369} + \sqrt {0.0615 + x} $$      = 37.25, the x is equal to ?
  1.    $${10^{ - 1}}$$
  2.    $${10^{ - 2}}$$
  3.    $${10^{ - 3}}$$
  4.    None of these
 Discuss Question
Answer: Option C. -> $${10^{ - 3}}$$
$$\eqalign{
& \Leftrightarrow 37 + \sqrt {0.0615 + x} = 37.25 \cr
& \Leftrightarrow \sqrt {0.0615 + x} = 0.25 \cr
& \Leftrightarrow 0.0615 + x = {\left( {0.25} \right)^2} = 0.0625 \cr
& \Leftrightarrow x = 0.001 \cr
& \Leftrightarrow x = \frac{1}{{{{10}^3}}} \cr
& \Leftrightarrow x = {10^{ - 3}} \cr} $$
Question 476. $$\sqrt {\frac{{0.0196}}{?}} = 0.2$$
  1.    0.49
  2.    0.7
  3.    4.9
  4.    None of these
 Discuss Question
Answer: Option A. -> 0.49
$$\eqalign{
& {\text{Let ,}} \cr
& \sqrt {\frac{{0.0196}}{x}} = 0.2 \cr
& {\text{Then,}} \cr
& \Leftrightarrow \frac{{0.0196}}{x} = 0.04 \cr
& \Leftrightarrow x = \frac{{0.0196}}{{0.04}} \cr
& \Leftrightarrow x = \frac{{1.96}}{4} \cr
& \Leftrightarrow x = 0.49 \cr} $$
Question 477. Three-fifth of the square of a certain number is 126.15. What is the numbers ?
  1.    14.5
  2.    75.69
  3.    145
  4.    210.25
 Discuss Question
Answer: Option A. -> 14.5
$$\eqalign{
& {\text{Let the number be }}x \cr
& {\text{Then,}} \cr
& \Leftrightarrow \frac{3}{5}{x^2} = 126.15 \cr
& \Leftrightarrow {x^2} = \left( {126.15 \times \frac{5}{3}} \right) \cr
& \Leftrightarrow {x^2} = 210.25 \cr
& \Leftrightarrow x = \sqrt {210.25} \cr
& \Leftrightarrow x = 14.5 \cr} $$
Question 478. If $$\sqrt {1 + \frac{x}{{169}}} {\text{ = }}\frac{{14}}{{13}}{\text{,}}$$    then x is equal to ?
  1.    1
  2.    13
  3.    27
  4.    None of these
 Discuss Question
Answer: Option C. -> 27
$$\eqalign{
& \Rightarrow \sqrt {1 + \frac{x}{{169}}} = \frac{{14}}{{13}} \cr
& \Rightarrow 1 + \frac{x}{{169}} = \frac{{196}}{{169}} \cr
& \Rightarrow \frac{x}{{169}} = \left( {\frac{{196}}{{169}} - 1} \right) \cr
& \Rightarrow \frac{x}{{169}} = \frac{{27}}{{169}} \cr
& \Rightarrow x = 27 \cr} $$
Question 479. If $$\sqrt {\left( {x - 1} \right)\left( {y + 2} \right)} = 7,$$     x and y being positive whole numbers, then the values of x and y respectively are ?
  1.    8, 5
  2.    15, 12
  3.    22, 19
  4.    None of these
 Discuss Question
Answer: Option A. -> 8, 5
$$\eqalign{
& \Leftrightarrow \sqrt {\left( {x - 1} \right)\left( {y + 2} \right)} = 7 \cr
& \Leftrightarrow \left( {x - 1} \right)\left( {y + 2} \right) = {\left( 7 \right)^2} \cr
& \Leftrightarrow \left( {x - 1} \right) = 7{\text{ and}}\left( {y + 2} \right) = 7 \cr
& \Leftrightarrow x = 8{\text{ and }}y = 5 \cr} $$
Question 480. The value of $$\sqrt 2 $$   up to three places of decimal is = ?
  1.    1.410
  2.    1.412
  3.    1.413
  4.    1.414
 Discuss Question
Answer: Option D. -> 1.414
$$\eqalign{
& \,\,\,\,\,\,\,\,\,\,1|\overline 2 \,.\,\,\overline {00} \,\,\overline {00} \,\,\overline {00} \,(1.414 \cr
& \,\,\,\,\,\,\,\,\,\,\,\,\,|1 \cr
& \,\,\,\,\,\,\,\,\,\,\,\,\,| - - - - - - - - \cr
& \,\,\,\,\,\,24|\,\,1\,00 \cr
& \,\,\,\,\,\,\,\,\,\,\,\,\,|\,\,\,\,96 \cr
& \,\,\,\,\,\,\,\,\,\,\,\,\,| - - - - - - - - \cr
& \,\,\,281\,|\,\,\,\,\,\,\,\,\,400 \cr
& \,\,\,\,\,\,\,\,\,\,\,\,\,|\,\,\,\,\,\,\,\,281 \cr
& \,\,\,\,\,\,\,\,\,\,\,\,\,| - - - - - - - \cr
& 2824\,|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,11900 \cr
& \,\,\,\,\,\,\,\,\,\,\,\,\,|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,11296 \cr
& \,\,\,\,\,\,\,\,\,\,\,\,\,| - - - - - - - \cr
& \therefore \sqrt 2 = 1.414 \cr} $$

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