A small terrace comprises of 10 steps each of which is 15m long and made of solid concrete. Each step has a rise of 0.25 m and a tread of 0.5m. The total volume of concrete required is -
Answer & explanation
Correct answer: option 4
Dimensions in 1st step = 15×0.25×0.5 m
Volume of first step = 1.875 cubic m
Dimensions of second step= 15×0.5×05m
Volume of 2nd step = 3.75 cubic m
Dimensions of 3rd step = 15×0.75×0.5 m
Volume of 3rd step = 5.625 cubic m
Now, we have
a= 1.875
d= 1.875 and n=15
Sum of 15 terms can be calculated as follows:
S15=\(\frac{15}{2}\)[2×1.875+14×1.875 ] = 225
Volume of concrete = 225 cubic m