Sum of the number of primes between 16–80 and 90–100 is
20
18
17
16
Step 1: List primes from 16 to 80.
Primes are numbers greater than 1 that have only two factors: 1 and the number itself.
Between 16 and 80, the primes are:
17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79
Count them:
There are 16 primes.
Step 2: List primes from 90 to 100.
Check numbers 90 to 100:
Only 97 is prime.
So there is 1 prime in this range.
Step 3: Add the two counts.
Total primes = 16 + 1 = 17.
Answer: 17 (Option C)