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

(a) 6

(b) 8

(c) 13

(d) 15

Correct Answer: (a) 6

#### Question from UPSC Prelims 2023 CSAT

**Explanation : **

## Pattern Analysis

The pattern here is to add all the numbers and then add the digits of the resulting sum.

Let’s look at the examples:

**7@9@10 = 8**

Add all numbers: 7 + 9 + 10 = 26

Add all digits: 2 + 6 = 8**9@11@30 = 5**

Add all numbers: 9 + 11 + 30 = 50

Add all digits: 5 + 0 = 5**11@17@21 = 13**

Add all numbers: 11 + 17 + 21 = 49

Add all digits: 4 + 9 = 13

Now, let’s apply this pattern to find the value of **23@4@15**:

Add all numbers: 23 + 4 + 15 = 42

Add all digits: 4 + 2 = **6**

So, **23@4@15 = 6**, which corresponds to option **(a)**.