It is 16. This is because there are five numbers between 11 and 16, and there are five numbers between 16 and 21 :]
Two.
There are no whole numbers between 20 and 21. Only fractions or decimals exist between these two numbers. Whole numbers between 20 and 25 are 21, 22, 23, and 24.
there are 39 whole numbers between 21 and 61
The prime numbers between 10 and 21 are 11, 13, 17, and 19.
5+5+5+5+1 That is only 5 numbers being added. There can be no answer for six numbers for the following reasons: The numbers are all odd. Two odd numbers make an even number. Two even numbers make an even number. 21 is odd. Take 6 odd numbers and add them up in pairs. Each pair of odd numbers gives an even number so there are 3 even numbers. Even + Even + Even = Even. So sum of any six odd numbers is even but 21 is not even.
The composite numbers between 21 and 31 are: 21 22 24 25 26 27 28 30
there is no fraction between the numbers 3 21 and 421
because in a mean for 7 with three numbers the total of the 3 numbers must be 21 and (even number) + (even number) = (even number) 21 is odd Q.E.D
23 and 29 are the only two numbers that fall between 21 and 30
composite numbers between 11 and 21:12 14 15 16 18
Four. The prime numbers between 10 and 21 are 11, 13, 17, and 19.