Question

The adjoining figure shows the cross section of a concrete wall to be constructed. It is 1.9 wide at the bottom, and 90 cm wide at the top and 5 m high. It its length is 20 m, find the cross sectional area

Answer 1

The cross sectional area is $7 cm ^2$.

Step-by-step explanation:

Given:

Wide at the bottom = 1.9 m

Wide at the top = 90 cm = 0.90           [1 m = 100 cm]

Height = 5 m

Length = 20 m

Now,

Cross sectional area = Area of trapezium = $\frac{1}{2} \times sum of parallel sides\times height$

                                                                     = $\frac{1}{2}\times (0.9 m +1.9m)\times 5$

                                                                     = $\frac{1}{2}\times (2.8 )\times 5$

                                                                     = $7 m^2$

Therefore, the cross sectional area is $7 cm ^2$