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UPSC Prelims 2023CSATQuantitative AptitudeNumber Series / Mathematical Operations

Q14. If 7  9  10 = 8, 9  11  30 = 5, 11  17  21 = 13, what is the value of 23  4  15 ?

A. 6✓ Correct
B. 8
C. 13
D. 15

Detailed Solution

✓ Correct Answer: Option A

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.

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