Answer:
300 bags of 20 kg of premixed are required.
Step-by-step explanation:
Given:
diameter of pond 'd'= 7 m (given)
radius of inner border of pond 'r'= d/2= 7/2 m
The radius of outer circular border 'R'= r+2= 7/2+2= 11/2m
Area of concrete border around the circular pond= area of outer circle- area of inner circle
So,
=> 22/7 x ((11/2)²-(7/2)²)
=> 22/7 x (121/4-49/4)
=>
=> 56.57 m²
volume of concrete needed= area x height= 56.57 x 0.05= 2.8285 cubic meter
Since 1 cube meter requires 106 x 20 kg bags,
2.8285 cubic meters require bags= 2.8285x106x20 kg
20 kg bags of premixed concrete required= 2.8285x106x20/20
=> 2.8285x106
=> 299.821 or 300 approximately