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8th Class Mathematics Mensuration Question Bank Mensuration

  • question_answer
    DIRECTIONS: Following questions consist of two statements, one labelled as the ?Assertion (A)? and other as ?Reason (R)?. You are to examine these two statements carefully and select the answer to these items using the code given below. Assertion (A): Area of the triangle having three sides 4 m, 6 m and 8 m is 135 sq. m. Reason (R): If a, b, c are the lengths of the sides of a triangle Area \[=\frac{1}{3}\pi {{r}^{2}}h=\frac{1}{3}\times \frac{22}{7}\times {{r}^{2}}\times 2=\frac{44{{r}^{2}}}{21}\] where \[\frac{44\times 64}{21}=\frac{44{{r}^{2}}}{21}\]

    A) Both A and R are individually true and R is the correct explanation of A.

    B) Both A and R are individually true but R is not the correct explanation of A.

    C)        A is true but R is false

    D) A is false but R is true.

    Correct Answer: C

    Solution :

    Assertion \[\frac{1}{3}rd\] \[=\pi {{r}^{2}}h-\frac{1}{3}\pi {{r}^{2}}h=\frac{2}{3}\pi {{r}^{2}}h=\frac{2}{3}\times \frac{22}{7}\times 6\times 6\times 14\] Area \[=1056c{{m}^{3}}.\] So, Assertion is incorrect. Reason is correct.


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