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The figure (ii) given below shows the cross section of a concrete wall to be constructed. It is 2 m wide at the top, 3.5 m wide at the bottom and its height is 6 m and its length is 400 m. Calculate

(i) the cross sectional area and

(ii) volume of concrete in the wall.

The figure shows the cross section of a concrete wall to be constructed. It is 2 m wide at the top, 3.5 m wide at the bottom and its height is 6 m and its length is 400 m. Calculate (i) the cross sectional area and (ii) volume of concrete in the wall. Mensuration, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

Mensuration

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Answer

Figure (ii) is a trapezium with parallel sides 2 m and 3.5 m

(i) Area of cross section = 12×\dfrac{1}{2} \times (sum of parallel sides) × height

= 12×\dfrac{1}{2} \times (2 + 3.5) × 6

= 12\dfrac{1}{2} × 5.5 × 6

= 5.5 × 3

= 16.5 m2.

Hence, area of cross-section = 16.5 m2.

(ii) Volume of concrete in the wall = Area of cross section × length

= 16.5 × 400

= 6600 m3.

Hence, volume of concrete wall = 6600 m3.

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