How many prime numbers are there between 30 to 85?
13
The correct answer is 13.
In our case, the largest number checked was 83. The square root of 83 is approximately 9.11. So, we only strictly needed to check divisibility by prime numbers up to 7 (the primes are 2, 3, 5, 7) for numbers in our range (after excluding obvious composite numbers like even numbers and multiples of 5). Our step-by-step check confirms these primes within the range.
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Important Questions from Prime Numbers
Which of the following is NOT a pair of co-prime numbers?
a and b are two positive integers such that the least prime factor of a is 2 and the least prime factor of b is 5. Then the least prime factor of a + b is
Which of the following is a pair of coprime numbers ?
If product of two prime numbers A and B (A < B) is 221, then what is the value of (4A – 3B)?
Sum of all the prime numbers between 70 and 100 is :
