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

let take clock strike at once 1+2+3+.......12=n(n+1)/2
clock strike twice 2+4+6+......+24=2(1+2+3+.....12)
=2(n(n+1)/2
=2 ×12×13/2
=156 times