10th Class Mathematics Triangles Question Bank MCQs - Triangles

  • question_answer
    The area of a right angled triangle is \[\text{4}0\text{ sq cm}\] and its perimeter is \[\text{4}0\text{ cm}\]. The length of its hypotenuse is:

    A) \[\text{16 cm}\]

    B) \[\text{18 cm}\]

    C) \[\text{17 cm}\]

    D) data insufficient.

    Correct Answer: B

    Solution :

    [b] Suppose hypotenuse of the triangle is c and other sides are a and b, obviously.
    \[c=\sqrt{{{a}^{2}}+{{b}^{2}}}\]
    We have,
    \[a+b+c=40\] and \[\frac{1}{2}ab=40\Rightarrow ab=80\]
    \[c=40-(a+b)\] and \[ab=80\]
    \[{{(a+b)}^{2}}-2\times 40(a+b)+1600={{a}^{2}}+{{b}^{2}}\]
    \[{{a}^{2}}+{{b}^{2}}+2\times 80-80(a+b)+1600={{a}^{2}}+{{b}^{2}}\]
    \[80(a+b-2)=1600\]
    \[a+b=22\]
    \[c=40-(a+b)\]
    \[=40-22=18\,cm\]


You need to login to perform this action.
You will be redirected in 3 sec spinner