0, 1, 3, 6, 10, 15, 21, 28, 36, 45, 55, 66, 78, 91, 105, 120, 136, 153
1'3'10 etc;
1, 3, 6, 10, 15, 21, 28, 36, 45, 55.
59
Look up a list of prime numbers (a Google search for "prime numbers" or "list of prime numbers" should do); every number (greater than 1) that is NOT a prime number is composite.
The average of the numbers 8, 12, 10, 15 and 7 is 10.4. To work this out, just add up the numbers in the list and divide them by the amount of numbers in the list.
1, 3, 6, 10, 15, 21, 28, 36
1,3,6,10,15,21,28,36,45,47,66,78,91,95
0,1,3,6,10,15,21,28,36,45,56,68,81,95,110,126,143,161,180,200. That's all the triangular numbers up to 200! I hope that's helped anyone with any thing.
166 and 167
45
1'3'10 etc;
28 and 10 are both triangular numbers and add up to 38
1,4,9,16,25,36,49,64,81,100,121,144,169,196,225,256,289,324,361,400 All the square numbers up to 20!
Formula for the nth Triangular Number: t(n) = 1/2n(n + 1) OR t(n) = (n2 + n)/2 t(0) = 0 t(1) = 1 t(2) = 3 t(3) = 6 t(4) = 10 t(5) = 15 t(6) = 21 t(7) = 28 t(8) = 36 t(9) = 45 t(10) = 55 t(11) = 66 t(12) = 78 t(13) = 91 t(14) = 104 t(15) = 120 For a more extensive list, or for more any more information about the Triangular Numbers, type "Triangular Numbers" into Google. You'll find lots of helpful websites there.
1, 3, 6, 10, 15, 21, 28, 36, 45, 55.
First, you add them all up. Then you divide what you've got by how much numbers you've got in the list.
2,3,5,7,11,13,17,19,23,29,31,37,39,41,43,47,51,53,57,59,61,67,71,73