15 = 111116 = 10000
17 = 10001
18 = 10010
19 = 10011
20 = 10100
Here are the binary numbers from zero to fifteen: 0 = 0000 1 = 0001 2 = 0010 3 = 0011 4 = 0100 5 = 0101 6 = 0110 7 = 0111 8 = 1000 9 = 1001 10 = 1010 11 = 1011 12 = 1100 13 = 1101 14 = 1110 15 = 1111
0000 0000 1111 1000F ( or 15) = 1111 in binary, and 8 = 1000 in binary, so F is 1111 1000
15 = 1111 14 = 1110 13 = 1101
The answer would be 15 and 21. The triangular numbers are 1,3,6,10,15,21,28,36,45,55,66,78. 15 plus 21 is 36 which is on the list. 21 minus 15 is 6 and that is on the list as well.
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.
The list of numbers that are divisible by five is infinite. The first four are: 5, 10, 15, 20 . . .
13, 15
The binary number 1111 = 15
The prime numbers between 15 and 30 are: 17, 19, 23 and 29
15 = 1111
6 8 9 10 12 14 15
No.