What is the sum of all digits in the telephone dial (0 to 9)?
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. 45.
We need the sum of digits from 0 to 9.
So, 0 + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9
Group them smartly:
(0 + 9) + (1 + 8) + (2 + 7) + (3 + 6) + (4 + 5)
= 9 + 9 + 9 + 9 + 9
= 5 × 9 = 45