They are: 43+47 = 90
172
The sum of the numbers from 1 to 20 inclusive is 220.
The sum of the numbers 1 through 27 is 378.
The sum of the numbers from 1 through 100 is 5,050.
91
-20
The sum of prime numbers between 90 and 100 is 97, the only prime number between 90 and 100.
They are: 43+47 = 90
172
The three composite numbers are 28, 30 and 32. Their sum is 90.
40 and 50
40 and 50
the highest sum of the numbers is 17 and the lowest is 1. The only perfect squares in that range are 1,4,9, and 16. That means the following numbers will work: 10,13.18,22,27,31,36,40,45,54,63,72,79,81,88, and 90; that is 16 numbers
The sum is 73+79+83+89 = 324
The sum of the numbers from 1 to 20 inclusive is 220.
The sum of the numbers 1 through 27 is 378.