Answer:
The teacher's age can be either 41 or 43 or 47
Explanation:
Given that age of a teacher is prime number between 40 and 50.
Here note that directly the teacher's age is not given but as a riddle using Mathematics.
Between 40 and 50 the teacher has an age which is a prime number.
So it is sufficient if we find all prime numbers between 40 and 50.
A prime number is one which has only itself and 1 as factors.
Keeping the above rule, we find that 40, 42, 44, 45, 46, 48, 49, 50 are divisible by some number other than 1.
Hence these are not prime
THe left overs are the prime numbers namely 41, 43, 47
So teacher's age can be any one of the 3, i.e. 41, 43, 47