Practice MCQ Questions and Answer on Area

161.

The area of two similar triangles are 12 cm² and 48 cm². If the height of the smaller one is 2.1 cm, then the corresponding height of the bigger one is :

(A) 0.525 cm
(B) 4.2 cm
(C) 4.41 cm
(D) 8.4 cm

Solution:

 Note : The areas of two similar triangles are in the ratio of the squares of the corresponding altitudes. Let the length of the required altitude be x cm Then, $$\eqalign{ & \frac{{12}}{{48}} = \frac{{{{\left( {2.1} \right)}^2}}}{{{x^2}}} \cr & \Rightarrow {x^2} = \left( {4.41 \times 4} \right) \cr & \Rightarrow x = 2.1 \times 2 \cr & \Rightarrow x = 4.2\,cm \cr} $$

162.

A tank is 25 m long, 12 m wide and 6 m deep. The cost of plastering its walls and bottom at 75 paise per sq. m, is:

(A) Rs. 456
(B) Rs. 458
(C) Rs. 558
(D) Rs. 568

Solution:

 $$\eqalign{ & {\text{Area}}\,{\text{to}}\,{\text{be}}\,{\text{plastered}} \cr & = \left[ {2\left( {l + b} \right) \times h} \right] + \left( {l \times b} \right) \cr & = \left\{ {\left[ {2\left( {25 + 12} \right) \times 6} \right] + \left( {25 \times 12} \right)} \right\}{m^2} \cr & = \left( {444 + 300} \right){m^2} \cr & = 744{m^2} \cr & \therefore {\text{Cost}}\,{\text{of}}\,{\text{Plastering}} \cr & = Rs.\,\left( {744 \times \frac{{75}}{{100}}} \right) \cr & = Rs.\,558 \cr} $$

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Practice MCQ Questions and Answer on Area

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