If a clock strikes once at 1 o’clock, twice at 2 o’clock and so on

1.	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» Number of times the clock strikes each hour form an A.P. Number of times strike in 12 hours is 1 + 2 + 3 + … + 12 Here, a = 1, d = 1, n = 12, l = 12 S_n = (n/2) (a + l) = (12/2) (1 + 12) = 6 x 13 = 78 times ∴ Number of times the clock strike in 24 hours = 78 x 2 = 156 times.

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»

Number of times the clock strikes each hour form an A.P.

Number of times strike in 12 hours is 1 + 2 + 3 + … + 12

Here, a = 1, d = 1, n = 12, l = 12

S_n = (n/2) (a + l) = (12/2) (1 + 12)

= 6 x 13 = 78 times

∴ Number of times the clock strike in 24 hours

= 78 x 2 = 156 times.