Given, Applying componendo and dividendo, we get : Hence, x = .

If two pipes function simultaneously, the reservoir will be filled in 12 hours. One pipe fills the empty reservoir 10 hours faster than the other. How many hours does it take the second pipe to fill the reservoir ?

The marks of 200 students are as given below :
Marks No. of students
20-29 7
30-39 11
40-49 20
50-59 46
60-69 57
70-79 37
80-89 15
90-99 7
Draw a cumulative frequency curve and find :
(i) median marks
(ii) if 80% of the students passed, find the passing marks.