Add 1+11+21+31+41 = 105
and  2+12+22+32+42 = 110
similarly
115
120
125
130
135
140
145
150
Now 10 x 100 = 1000
5x5 = 25
2x10+2x20+2x30+2x40+50=250
add together 1275

May be lengthy and you may have different solution