Answer :

To determine which number John does not like, we need to look for a pattern in the numbers he likes and dislikes. By examining the examples provided:

1. John likes 400 but not 300:
- 400: Sum of digits is 4 (4 + 0 + 0 = 4).
- 300: Sum of digits is 3 (3 + 0 + 0 = 3).

2. John likes 100 but not 99:
- 100: Sum of digits is 1 (1 + 0 + 0 = 1).
- 99: Sum of digits is 18 (9 + 9 = 18).

3. John likes 2500 but not 2400:
- 2500: Sum of digits is 7 (2 + 5 + 0 + 0 = 7).
- 2400: Sum of digits is 6 (2 + 4 + 0 + 0 = 6).

From these observations, we see that John does not have a fixed pattern in the sum of digits being liked or disliked. However, for each set, he prefers specific sums over others.

Now, let's apply this understanding to the given options:

1. Option (a): 900
- Sum of digits: 9 (9 + 0 + 0 = 9)

2. Option (b): 1000
- Sum of digits: 1 (1 + 0 + 0 + 0 = 1)

3. Option (c): 1100
- Sum of digits: 2 (1 + 1 + 0 + 0 = 2)

4. Option (d): 1200
- Sum of digits: 3 (1 + 2 + 0 + 0 = 3)

Based on these calculations, we find:

- 900 has a sum of digits equal to 9
- 1000 has a sum of digits equal to 1
- 1100 has a sum of digits equal to 2
- 1200 has a sum of digits equal to 3

Given the provided solution, John does not like any options:

- He neither likes 900 (sum is 9)
- Nor 1000 (sum is 1)
- Nor 1100 (sum is 2)
- Nor 1200 (sum is 3)

So, the correct answer is that John does not like any of these numbers:

[a] 900
[b] 1000
[c] 1100
[d] 1200