Average of the first 'n' natural numbers = (n + 1)/2
We get (9 + 1)/2 = 5
Find the average of the first 9 natural numbers?
Options:
(A) 8
(B) 5
(C) 10
(D) 11
(E) 12
(B)

1 minute’s work of both the punctures = (1⁄9 + 1⁄6) = 5⁄18
So, both the punctures will make the tyre flat in 18⁄5 = 33⁄5 min.
A tyre has two punctures. The first puncture along would have made the tyre flat in 9 minutes and the second alone would have done it in 6 minutes. If air leaks out at a constant rate, how long does it take both the punctures together to make it flat?
Options:
(A) 1 1⁄2 minutes
(B) 3 1⁄2 minutes
(C) 3 3⁄5 minutes
(D) 4 1⁄4 minutes
(E) None of these
(C)

(1056 / 23) gives remainder 21
21 + 2 = 23, So we need to add 2

What is theleast number should be added to 1056, so the sum of the number is completely divisible by 23?
Options:
(A) 1
(B) 2
(C) 5
(D) 6
(E) 8
(B)