9. A cistern of capacity 8000 litres measures externally 3.3 m by 2.6 m by 1.1 m and its walls are 5 cm thick. The thickness of the bottom is:
A. 90 cm
B. 1 dm
C. 1 m
D. 1.1 cm
Answer:
Option : B
Let the thickness of the bottom be a cm.
Then, [(330 - 10) x (260 - 10) x (110 - a)] = 8000 x 1000
⇒ 320 x 250 x (110 - a) = 8000 x 1000
⇒
|
(110 - a) =
|
|
8000 x 1000
|
|
=
|
100 cm
|
320 x 250
|
⇒ a = 10 cm = 1 dm
