Three of the following four number-pairs are alike in a certain way and thus form a group. Which is the pair that does not belong to that group?

**(NOTE : Operations should be performed on the whole numbers, without breaking down the numbers into its constituent digits. E.g. 13 – Operations on 13 such as adding/subtracting/multiplying etc. to 13 can be performed. Breaking down 13 into 1 and 3 and then performing mathematical operations on 1 and 3 is not allowed.)**

Question

Three of the following four number-pairs are alike in a certain way and thus form a group. Which is the pair that does not belong to that group?

**(NOTE : Operations should be performed on the whole numbers, without breaking down the numbers into its constituent digits. E.g. 13 – Operations on 13 such as adding/subtracting/multiplying etc. to 13 can be performed. Breaking down 13 into 1 and 3 and then performing mathematical operations on 1 and 3 is not allowed.)**

Accepted Answer

**Solution:**

1. Analyze the relationship between the numbers in each pair.

2. Check if the second number is a multiple of the first number by 9:
   - Pair 1: $117 \div 13 = 9$ (exact)
   - Pair 2: $89 \div 11 \approx 8.09$ (not an integer)
   - Pair 3: $162 \div 18 = 9$ (exact)
   - Pair 4: $135 \div 15 = 9$ (exact)

3. Since pairs 1, 3, and 4 follow the pattern where the second number is 9 times the first, pair 2 does not fit.

**Answer:** The pair that does not belong to the group is **2. 11-89**.

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