If 7  9  10 = 8, 9  11  30 = 5, 11  17  21 = 13, what is the value of 23  4  15 ?

1. A. 6
2. B. 8
3. C. 13
4. D. 15

Answer: A

Explanation

Let’s analyze the given operations to find the pattern:
1. 7  9  10: Sum = 7 + 9 + 10 = 26. The result is 8, which is the sum of the digits of 26 (2+6=8).
2. 9  11  30: Sum = 9 + 11 + 30 = 50. The result is 5, which is the sum of the digits of 50 (5+0=5).
3. 11  17  21: Sum = 11 + 17 + 21 = 49. The result is 13, which is the sum of the digits of 49 (4+9=13).

The pattern is to sum all the numbers involved in the operation, and then sum the digits of that total sum. Applying this to the final expression:
23  4  15: Sum = 23 + 4 + 15 = 42.
Sum of the digits of 42 = 4 + 2 = 6.
Therefore, the value is 6.