Question

Three numbers between 80 and 100 are prime numbers. What numbers are they? Eight numbers between 31 and 41 are composite numbers what are they? Write all the prime numbers that are odd between 30 to 50. Write all the Prime numbers that are even from 30 to 50. Write all the composite numbers that are odd between 30 to 50. Write all the composite numbers that are even between 30 to 50. Describe two different ways to find 2×50×25 using mental math.

Answer 1

83, 89, and 97 are three primes between 80 and 100.

The primes between 30 and 50 are 31, 37, 41, 43, and 47, all of which are odd.  All other numbers between 30 and 50 are composite.

To mentally find 2*50*25, you could either first multiply 25 by 2, to get 50*50, which can easily be calculated as 2500, or you could multiply the 50 by 2, for a result of 100*25, which is clearly also 2500.