A farmer has 10 cows. All cows died except four. How many cows are left? 

1. 4 
2. 5 
3. 6 
4. None of these 

Explanation:

The key word in the sentence is “except“. When it says “All cows died except four,” it means that out of the initial 10 cows, only 4 survived. The rest (10 – 4 = 6) died.

Therefore, the number of cows left alive is four