100
5050
102*25=2550
62.5 and 37.5
if you add all the numbers up and dived them by the numbers of numbers
100
5050
-99
102*25=2550
5050, ie (1 + 100) x (100/2)
You can either just add them up or use quick logic to add them in pairs: All the numbers from 1 to 49 match up with 51 through 99 to = 49 pairs of 100 = 4900, than add the two you skipped 4900 + 50 + 100 = 5050 total
36 and 64
103
30
53+47
The even numbers up to 100 are: 2 468101214161820222426283032343638404244464850525456586062646668707274767880828486889092949698100.
62.5 and 37.5