What are the first 25 numbers added together?

1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 + 11 + 12 + 13 + 14 + 15 + 16 + 17 + 18 + 19 + 20 + 21 + 22 + 23 + 24 + 25 = 325

1 + 2 = 3
3 + 3 = 6
6 + 4 = 10
10 + 5 = 15
15 + 6 = 21
21 + 7 = 28
28 + 8 = 36
36 + 9 = 45
45 + 10 = 55
55 + 11 = 66
66 + 12 = 78
78 + 13 = 91
91 + 14 = 105
105 + 15 = 120
120 + 16 = 136
136 + 17 = 153
153 + 18 = 171
171 + 19 = 190
190 + 20 = 210
210 + 21 = 231
231 + 22 = 253
253 + 23 = 276
276 + 24 = 300
300 + 25 = 325

The first 25 numbers added together equal 325.