A tank is 7m long and 4m wide at what speed should water run through pipes 5cm broad and 4cm deep so that in 6 hours and 18 minutes, the water level in the tank rises by 4.5cm?

A. 720
B. 1440
C. 1860
D. 2160
In the word, “MATERIAL” there are three vowels A, I, E.
If all the vowels are together, the arrangement is MTRL’AAEI’.
Consider AAEI as one unit. The arrangement is as follows.
M T R L A A E I
The above 5 items can be arranged in 5! ways and AAEI can be arranged among themselves in 4!/2! ways.
Number of required ways of arranging the above letters = 5! * 4!/2!
= (120 * 24)/2 = 1440 ways.