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Rational Numbers Test - 28

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Rational Numbers Test - 28
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  • Question 1
    1 / -0
    Find 33 rational numbers between 00 and 11.
    Solution
    The mean of 00 and 1 1 is 0+12=12\cfrac{0+1}{2}=\cfrac{1}{2}.

    The mean of 00 and 12 \cfrac{1}{2} is (0+12)÷2=12÷2=12×12=14\begin{pmatrix}0+\cfrac{1}{2}\end{pmatrix}\div2=\cfrac{1}{2}\div2=\cfrac{1}{2}\times\cfrac{1}{2}=\cfrac{1}{4}

    The mean of 12\cfrac{1}{2} and 1 1 is (12+1)÷2\begin{pmatrix}\cfrac{1}{2}+1\end{pmatrix}\div2

    =(1+22)÷2=32÷2=32×12=34=\begin{pmatrix}\cfrac{1+2}{2}\end{pmatrix}\div2=\cfrac{3}{2}\div2=\cfrac{3}{2}\times\cfrac{1}{2}=\cfrac{3}{4}.

    So, the 33 rational numbers between 00 and 1 1 are 12,14\cfrac{1}{2},\,\cfrac{1}{4} and 34 \cfrac{3}{4}.
  • Question 2
    1 / -0
    Choose the rational number which does not lie between rational numbers 25-\cfrac {2}{5} and 15-\cfrac {1}{5}
    Solution
    Since the given rational numbers 25-\dfrac {2}{5} and 15-\dfrac {1}{5} are negative rational numbers, therefore, none of the positive rational number can lie between them.

    Hence, the rational number 310\dfrac {3}{10} does not lie between the rational numbers 25-\dfrac {2}{5} and 15-\dfrac {1}{5} 
  • Question 3
    1 / -0
    If DD be subset of the set of all rational  numbers, then DD is closed under the binary operations of ..............
    Solution

    Rational numbers are closed under all these operations except for division. Add two rational numbers, get a rational number; multiply two rationals, get a rational, etc. Problem with division is that if we divide any number by '0' we cannot tell the output. Some people says it is infinity but that's not true. Division by '0' is not defined.

    So correct answer will be option C

  • Question 4
    1 / -0
    Find five rational numbers between 32\displaystyle\frac{-3}{2} and 53\displaystyle\frac{5}{3}.
    Solution
    Converting the given rational numbers with the same denominators 
    32=3×32×3=96\cfrac{-3}{2}=\cfrac{-3\times3}{2\times3}=\cfrac{-9}{6} and 53=5×23×2=106\cfrac{5}{3}=\cfrac{5\times2}{3\times2}=\cfrac{10}{6}

    We know that 9<8<7<6<<0<1<2<8<9<10-9\,<\,-8\,<\,-7\,<\,-6\,<\,\dots\,<\,0\,<\,1\,<\,2\,<\,8\,<\,9\,<\,10
    96<86<76<66<<06<16<26<<86<96<106\Rightarrow\cfrac{-9}{6}\,<\,\cfrac{-8}{6}\,<\,\cfrac{-7}{6}\,<\,\cfrac{-6}{6}\,<\,\dots\,<\,\cfrac{0}{6}\,<\,\cfrac{1}{6}\,<\,\cfrac{2}{6}\,<\,\dots\,<\,\cfrac{8}{6}\,<\,\cfrac{9}{6}\,<\,\cfrac{10}{6}.

    Thus, we have the following five rational numbers between 32\cfrac{-3}{2} and 53\cfrac{5}{3} 
    86,76,06,16and26\Rightarrow \cfrac{-8}{6},\,\cfrac{-7}{6},\,\cfrac{0}{6},\,\cfrac{1}{6}and\cfrac{2}{6}
  • Question 5
    1 / -0
    Find 99 rational numbers between 19  and  15-\displaystyle\frac{1}{9}\;and\;\displaystyle\frac{1}{5}.
    Solution
    Convert the rational numbers into equivalent rational numbers with the same denominator.

    LCM of 99 and 55 is 4545.

    19=1×59×5=545-\displaystyle\frac{1}{9}=\displaystyle\frac{-1\times5}{9\times5}=\displaystyle\frac{-5}{45} and 15=1×95×9=945\displaystyle\frac{1}{5}=\displaystyle\frac{1\times9}{5\times9}=\displaystyle\frac{9}{45}

    The integers between 5-5 and 99 are
    4,3,2,1,0,1,2,3,4,5,6,7,8-4,\,-3,\,-2,\,-1,\,0,\,1,\,2,\,3,\,4,\,5,\,6,\,7,\,8.

    The corresponding rational numbers are 445,345,245,145,045,145,245,345,445,545,645,745,845\displaystyle\frac{-4}{45},\,\displaystyle\frac{-3}{45},\,\displaystyle\frac{-2}{45},\,\displaystyle\frac{-1}{45},\,\displaystyle\frac{0}{45},\,\displaystyle\frac{1}{45},\,\displaystyle\frac{2}{45},\,\displaystyle\frac{3}{45},\,\displaystyle\frac{4}{45},\,\displaystyle\frac{5}{45},\,\displaystyle\frac{6}{45},\,\displaystyle\frac{7}{45},\,\displaystyle\frac{8}{45}

    On selecting any 99 of them, we get 99 rational numbers between 19-\displaystyle\frac{1}{9} and 15\displaystyle\frac{1}{5} as

    445,345,245,145,245,345,445,545,845\displaystyle\frac{-4}{45},\,\displaystyle\frac{-3}{45},\,\displaystyle\frac{-2}{45},\,\displaystyle\frac{-1}{45},\,\displaystyle\frac{2}{45},\,\displaystyle\frac{3}{45},\,\displaystyle\frac{4}{45},\,\displaystyle\frac{5}{45},\,\displaystyle\frac{8}{45}
  • Question 6
    1 / -0
    Write any 1010 rational numbers between 0  and  20\;and\;2.
    Solution
    Let us write 00 as 010\dfrac{0}{10} and 22 as 2010.\dfrac{20}{10}.


    So, ten rational numbers between these will be,
    110,  210,  310,  410,  510,  610,  710, 810, 910,  1\dfrac{1}{10},\;\dfrac{2}{10},\;\dfrac{3}{10},\;\dfrac{4}{10},\;\dfrac{5}{10},\;\dfrac{6}{10},\;\dfrac{7}{10},\ \dfrac{8}{10},\ \dfrac{9}{10},\; 1

    Hence, option DD is correct.
  • Question 7
    1 / -0
    For rational numbers ab\dfrac {a}{b} and pq\dfrac {p}{q}, where a,b,p,qQa, b, p, q\in Q and .............. condition exists, then they are closed under division.
    Solution
    The numbers a÷0a\div 0 and p÷0p\div 0 are not rational numbers. So, for any rational numbers of the forms ab\dfrac {a}{b} and pq\dfrac {p}{q} where b0b\neq 0 and q0q\neq 0 and a,b,p,qa, b, p, q are rational numbers, they are closed under division.
  • Question 8
    1 / -0
    Simplify using associative property :
    716×(2449×2815)\dfrac {7}{16} \times \left (\dfrac {-24}{49} \times \dfrac {28}{15}\right )
    Solution
    716×(2449×2815)=(716×2449)×2815\dfrac {7}{16} \times \left (\dfrac {-24}{49} \times \dfrac {28}{15}\right ) = \left (\dfrac {7}{16}\times \dfrac {-24}{49}\right ) \times \dfrac {28}{15} (associative property)

    =(12×37)×2815= \left (\dfrac {1}{2} \times \dfrac {-3}{7}\right )\times \dfrac {28}{15}

    =314×2815= \dfrac {-3}{14} \times \dfrac {28}{15}

    =25= \dfrac {-2}{5}
  • Question 9
    1 / -0
    Simplify using associative property :
    89×(2732×821)\dfrac {-8}{9}\times \left (\dfrac {27}{32} \times \dfrac {-8}{21}\right )
    Solution
    89×(2732×821)=(89×2732)×821\dfrac {-8}{9}\times \left (\dfrac {27}{32} \times \dfrac {-8}{21}\right ) = \left (\dfrac {-8}{9} \times \dfrac {27}{32}\right ) \times \dfrac {-8}{21} (\because associative property)
    =(34)×821= \left (\dfrac {-3}{4}\right ) \times \dfrac {-8}{21}
    =+27= \dfrac {+2}{7}
  • Question 10
    1 / -0
    Choose the rational number which does not lie between rational numbers 25\displaystyle-\frac{2}{5} and 15\displaystyle-\frac{1}{5}
    Solution

    Consider given the rational numbers25-\dfrac{2}{5} and 15-\dfrac{1}{5}

    Now, given both rational numbers are negative numbers so the number which lies between them will be negative.

    So,310\dfrac{3}{10} will not lie between them,

    Hence, this is the answer.

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