9th Class Mathematics Heron's Formula Question Bank Herons Formula

  • question_answer
    A design is made on a rectangular tile of dimensions\[50\,cm\,\times \,70\,cm\]as shown in figure. The design shows 8 triangles, each of sides 26 cm, 17 cm and 25 cm. Find the total area of the design and the remaining area of the tile respectively.

    A) \[1632\,c{{m}^{2}},1886\,c{{m}^{2}}\]

    B)        \[1538\,c{{m}^{2}},1632\,c{{m}^{2}}\]

    C)        \[1632\,c{{m}^{2}},1868\,c{{m}^{2}}\]

    D)         \[1538\,c{{m}^{2}},1632\,c{{m}^{2}}\]  

    Correct Answer: C

    Solution :

    Area of rectangular tile \[=(50\times 70)c{{m}^{2}}=3500\,c{{m}^{2}}\] We have, \[a=25\,cm,\,b=17\,cm\]and \[c=26\,cm\] \[\therefore \]\[s=\frac{a+b+c}{2}=\left( \frac{25+17+6}{2} \right)\,cm\] = 34 cm \[\therefore \]Area of 1 triangular tile \[=\sqrt{s(s-a)(s-b)(s-c)}\] \[=\sqrt{34(34-25)(34-17)(34-26)}\,c{{m}^{2}}\] \[=\sqrt{34\times 9\times 17\times 8}\,c{{m}^{2}}=204\,c{{m}^{2}}\] \[\therefore \]Total area of 8 triangles \[=(204\times 8)c{{m}^{2}}\] \[=1632\,c{{m}^{2}}\] So, area of the design \[=1632\,c{{m}^{2}}\] Also, remaining area of the tile \[=(3500-1632)\,c{{m}^{2}}=1868\,c{{m}^{2}}\]      


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