4950
-99
-99
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
There are 90 two-digit numbers in the set of natural numbers. These numbers range from 10 to 99, inclusive. To find the total, you can subtract the smallest two-digit number (10) from the largest (99) and add one: (99 - 10 + 1 = 90).
It is instructive to note that you can rewrite 1+2+3+4....+99+100 as 1+100+2+99+3+98....+50+51 Then you can group each pair of numbers as (1+100)+(2+99)+(3+98)+...+(50+51) All of these couplets add up to 101, and there are 50 of them. Thus the sum of the first 100 whole numbers is 50x101. This can be calculated at 5,050.
-99
-99
66+.99 1+65.99 There's an infinite number of combinations
-99
-99
4700
It's simple: 1-49 matches up with 51-99 to add up to 100- 4900 50 100 5050 is the answer.
-99
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
102
99
-99