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Quantitative Aptitude

SURDS AND INDICES MCQs

Surds & Indices, Indices And Surds, Power

Total Questions : 753 | Page 5 of 76 pages
Question 41.

\(\frac{1}{1+a^{(n-m)}}+\frac{1}{1+a^{(m-n)}} = ?\)

  1.    0
  2.    \(\frac{1}{2}\)
  3.    1
  4.    am + n
 Discuss Question
Answer: Option C. -> 1

\(\frac{1}{1+a^{(n-m)}}+\frac{1}{1+a^{(m-n)}} = \frac{1}{\left(1+\frac{a^{n}}{a^{m}}\right)} + \frac{1}{\left(1+\frac{a^{m}}{a^{n}}\right)}\)


\(\frac{a^{m}}{\left(a^{m}+a^{n}\right)}+\frac{a^{n}}{\left(a^{m}+a^{n}\right)}\)


= \(\frac{{\left(a^{m}+a^{n}\right)}}{{\left(a^{m}+a^{n}\right)}}\)


= 1.

Question 42.

If m and n are whole numbers such that mn = 121, the value of (m - 1)n + 1 is:

  1.    1
  2.    10
  3.    121
  4.    1000
 Discuss Question
Answer: Option D. -> 1000

We know that 112 = 121.


Putting m = 11 and n = 2, we get:


(m - 1)n + 1 = (11 - 1)(2 + 1) = 103 = 1000.

Question 43.

\(\left(\frac{x^{b}}{x^{c}}\right)^{(b+c-a)}.\left(\frac{x^{c}}{x^{a}}\right)^{(c+a-b)}. \left(\frac{x^{a}}{x^{b}}\right)^{(a+b-c)} = ?\)

  1.    xabc
  2.    1
  3.    xab + bc + ca
  4.    xa + b + c
 Discuss Question
Answer: Option B. -> 1

Given Exp. = \(x^{(b-c)(b+c-a)}.x^{(c-a)(c+a-b)}.x^{(a-b)(a+b-c)}\) 


= \( x^{(b-c)(b+c)-a(b-c)}. x^{(c-a)(c+a)-b(c-a)}. x^{(a-b)(a+b)-c(a-b)}\)


= \(x^{(b^{2}-c^{2}+c^{2}-a^{2}+a^{2}-b^{2})} . x^{-a(b-c)-b(c-a)-c(a-b)}\)


= \(\left(x^{0}\times x^{0}\right)\)


= \(\left(1\times1\right) = 1\)


 


 

Question 44.

If x = 3 + 22, then the value of  \(\left(x-\frac{1}{x}\right)\) is :

  1.    1
  2.    2
  3.    22
  4.    33
 Discuss Question
Answer: Option B. -> 2

\(\left(x-\frac{1}{x}\right)^{2} = x+\frac{1}{x}-2\)


= (3 + 22) + \(\frac{1}{(3+22)}-2\)


= (3 + 22) + \(\frac{1}{(3+22)}-2\times \frac{{(3-22)}}{{(3-22)}}-2\)


= (3 + 22) + (3 - 22) - 2


   = 4.


Therefore \(\left(x-\frac{1}{x}\right) = 2.\)

Question 45. (17)3.5 × (17)? = 178
  1.    2.29
  2.    2.75
  3.    4.25
  4.    4.5
 Discuss Question
Answer: Option D. -> 4.5
Question 46. Given that 100.48 = x, 100.70 = y and xz = y2, then the value of z is close to:
  1.    1.45
  2.    1.88
  3.    2.9
  4.    3.7
 Discuss Question
Answer: Option C. -> 2.9
Question 47. $${\text{If}}\,{\kern 1pt} {\left( {\frac{a}{b}} \right)^{x - 1}} = {\left( {\frac{b}{a}} \right)^{x - 3}},$$     then the value of x is
  1.    $$\frac{1}{2}$$
  2.    1
  3.    2
  4.    $$\frac{7}{2}$$
 Discuss Question
Answer: Option C. -> 2
Question 48. If 5a = 3125, then the value of 5(a - 3) is:
  1.    25
  2.    125
  3.    625
  4.    1625
 Discuss Question
Answer: Option A. -> 25
Question 49. If 3(x - y) = 27 and 3(x + y) = 243, then x is equal to:
  1.    0
  2.    2
  3.    4
  4.    6
 Discuss Question
Answer: Option C. -> 4
Question 50. (256)0.16 × (256)0.09 = ?
  1.    4
  2.    16
  3.    64
  4.    256.25
  5.    None of these
 Discuss Question
Answer: Option A. -> 4

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