Question

A well having 10m inside diameter is dug 8.4m deep. Earth taken out of it is spread all around it to a width of 7.0m to form a beautiful embankment. Find the height of the embankment. The contractor charged Rs. 500 per cubic metre for digging and making the circular embankment. He measured height of the embankment as 2m. How much extra money he made?

Answer 1

Volume of earth = 22/7 x 5² x 8.4 = 660m³
Volume of embankment = 22/7 R²h - 22/7r²h = 660
    h(22/7R² -22/7r²) = 660
   h (22/7 x 12² - 22/7x5²) = 660
374h = 660
h = 1.765m

Total charge = 2x660x500 = Rs. 660000
Amount charged by contractor = 500x660 + (22/7x12²x3.765 - 22/7x5²x3.765)x500 = 330000 + 704055
= 1034055

Extra money made = 1034055 - 660000 - Rs. 374055