A clock strikes once at 1o' clock, twice at 2 o' clock, ....., twelve times at 12o, clock. How many times will the bell strike in course of 2 days?

A clock strikes once at 1o' clock, twice at 2 o' clock, ....., twelve times at 12o, clock. How many times will the bell strike in course of 2 days? Correct Answer 312

Given:

A clock strikes once at 1o' clock, twice at 2 o' clock, ....., twelve times at 12o, clock.

So, series so formed =  

We know, 1 day = 24 hours, but a clock has just 12 hours so we, will multiply the series by 2.

New series = 2 

As, Sum of n terms = n/2

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

 S₁₂ = 2 × 12/2

S₁₂ = 2 × 6 × 13

S₁₂ = 156

So, the clock will strike "156" times a day.

So, In 2 days the clock will strike 156 × 2 = '312 times'.

Hence, "312" is the correct answer.