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A clock strikes once at 1 o'clock, twice at 2 o'clock, thrice at 3 o'clock and so on. What is the total number of strikings in a day = ?
Answer & Solution
Answer: Option
C
Solution:
Total number of strikings
$$\eqalign{ & = 2\left( {1 + 2 + 3 + ..... + 12} \right) \cr & = 2 \times \frac{{12 \times 13}}{2} \cr & = 156 \cr} $$
$$\eqalign{ & = 2\left( {1 + 2 + 3 + ..... + 12} \right) \cr & = 2 \times \frac{{12 \times 13}}{2} \cr & = 156 \cr} $$