Class 8 Rational Numbers CBSE Questions & Answers

Class 8 · Rational Numbers

This is Mathematics Class 8 Rational Numbers CBSE Questions & Answers. There are 15 questions in this test with each question having around four answer choices.

Questions & Answers

1
How many numbers in the following list are irrational? \(\sqrt 3 ,\pi ,e,\frac{1}{3},\sqrt[5]{3},\sqrt {49} ,\frac{{22}}{7},0\)
  • A
    3
  • B
    6
  • C
    4
    Correct
  • D
    5
2
Between two rational numbers
  • A
    there are infinitely many rational numbers
    Correct
  • B
    there is exactly one rational number
  • C
    there are only rational numbers and no irrational numbers
  • D
    there is no rational number
3
The product of any two irrational numbers is
  • A
    always an irrational number
  • B
    sometimes rational, sometimes irrational
    Correct
  • C
    always an integer
  • D
    always a rational number
4
Who was the first Mathematician to compute digits in the decimal expansion of\(\pi \)?
  • A
    Aryabhatta
  • B
    Dedekind
  • C
    Cantor
  • D
    Archimedes
    Correct
5
If a =2 and b = 3, then value of\({\left( {\frac{1}{a} + \frac{1}{b}} \right)^a}\).
  • A
    \(\frac{{25}}{{26}}\)
  • B
    \(\frac{{25}}{{36}}\)
    Correct
  • C
    \(\frac{{25}}{{26}}\)
  • D
    \(\frac{{24}}{{26}}\)
6
The two irrational numbers between \(\sqrt 2 \) and \(\sqrt 3 \)are
  • A
    1.5010010001………. And 1.601001000100001……
    Correct
  • B
    1.3010010001………. And 1.601001000100001……
  • C
    1.5010010001………. And 1.801001000100001……
  • D
    1.3010010001………. And 1.601001000100001……
7
Find the value of \(\frac{{{a^{ - 1}}}}{{{a^{ - 1}} + {b^{ - 1}}}} + \frac{{{a^{ - 1}}}}{{{a^{ - 1}} - {b^{ - 1}}}}\)
  • A
    \(\frac{{2{b^2}}}{{{b^2} + {a^2}}}\)
  • B
    \(\frac{{2{a^2}}}{{{b^2} - {a^2}}}\,\)
  • C
    \(\frac{{2{b^2}}}{{{b^2} - {a^2}}}\)
    Correct
  • D
    \(\frac{{2ab}}{{{b^2} - {a^2}}}\)
8
If r is a rational number and s is an irrational number, then r+s and r-s are ______.
  • A
    rationals
  • B
    irrationals
    Correct
  • C
    none of these
  • D
    natural number
9
If \(\frac{1}{x} = \frac{{{x^2}}}{{27}}\), then x is ________ number.
  • A
    none of these
  • B
    irrational
  • C
    negative
  • D
    rational
    Correct
10
\(\sqrt {45} \)is ________ number.
  • A
    rational
  • B
    none of these
  • C
    negative
  • D
    irrational
    Correct
11
\(\sqrt {80} \)is ________ number.
  • A
    negative
  • B
    rational
  • C
    none of these
  • D
    irrational
    Correct
12
Find the decimal representation of \(\frac{8}{3}\).
  • A
    2
  • B
    \(2.\overline 6 \)
    Correct
  • C
    3.7
  • D
    2.6
13
Express \(\frac{7}{8}\) in the decimal form.
  • A
    0.67
  • B
    0.875
    Correct
  • C
    20
  • D
    0.8
14
Find: \({\left( {\frac{{64}}{{25}}} \right)^{ - \frac{3}{2}}}\).
  • A
    125
  • B
    \(\frac{{125}}{{512}}\)
    Correct
  • C
    64
  • D
    512
15
What can the maximum number of digits be in the repeating block of digits in the decimal expression of\(\frac{1}{{17}}\)?
  • A
    10
  • B
    96
    Correct
  • C
    90
  • D
    9