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8th Class Mathematics Related to Competitive Exam Question Bank Arithmetic

  • question_answer
    Consider the following statements. (I) If a sum of money is lent at simple interest, then the: (II) Money gets doubled in 5 years if the rate of interest is \[{{R}_{1}}%\] (III) Money gets doubled in 5 years if the rate of interest 20%                                           (IV) Money becomes four times in 10 years if it gets doubled in 5 years. Which of the above statements is/are correct?

    A) I and III                 

    B) Only II

    C) III alone                 

    D) II and III      

    Correct Answer: B

    Solution :

    16.66% means it will be 83.33% of principal. For any amounts x, SI after 5 years at the rate of 5% is \[\left( 15+4-\frac{15\times 4}{100} \right)=19-\frac{60}{100}=19-\frac{3}{5}=19-0.6=18.4%\] \[\text{S}\text{.P}\text{.=M}\text{.P}\text{. }\!\!\times\!\!\text{ }\left\{ \frac{\text{100 - Discount }\!\!%\!\!\text{ }}{\text{100}} \right\}\] Amount = 2x. III. After 10 yrs. interest will be \[{{a}_{13}}=450-372=78\]so amount will be thrice i.e., 3x.


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