Question

16. A rectangular field is 30 metres long and 20 metres
wide. How much deep, it should be dug so that a 5
m long, 5.5 m wide and 1.5 m high solid can be
made from the earth taken out of the pit while the
volume of earth is increased by 10% -​

Answer 1

Answer:

Volume of well =πr

2

h=

7

22

×3.5×3.5×10=385m

3

Volume of earth dugout = Volume of well =385m

3

Area of remaining field = Area of field - Area of well

=30×20−π(3.5)

2

=600−

7

22

×3.5×3.5=600−38.5=561.5m

2

Now, increase in level of remaining field × Area of remaining field = Volume of earth dugout

⇒Riseinlevel=

Areaofremainingfield

Volumeofearthdaugout

=

561.5

385

=0.686m=68.6cm