Question

if a clock strikes once at 1 o'clock, twice at 2 o'clock and so on, how many times will it strike in a day?

Answer 1

The clock strikes n times in the nth hour
In 1st hour once
Twice in second hour
Thrice in third hour
And so on
So there are 12 hours in a day
Thus in a day it will strike 1+2+3+4+5+6+7+8+9+10+11+12 times a day
Thus it will strike 78 times a day

Answer 2

The formula is 2 * n/2(a+l)

                      = 2 * 12/2 * (1+12)

                      = 12 * 13

                      = 156.


Hope this helps!