Simple calculation 81 + 9 × 91 125 × 888 36 × 111 + 888 × 8

Simple calculation 81 + 9 × 91 125 × 888 36 × 111 + 888 × 8

81+9×91
=9×9+9×91
=9×(9+91)
=9×100
=900
125×888
=125×（800+80+8）
=125×800+125×80+125×8
=100000+10000+1000
=111000
36×111+888×8
=36×111+111×64
=111×（36+64）
=111×100
=11100

1+11+21+31+.+101+111

=(111+1)+(11+101)+.+(51+61)=112*6=672

How to calculate 1 + 11 + 21 + 31 +... + 101 + 111

Original formula = 1 + 10 + 1 + 20 + 1 + 30 + 1 + +100+1+100+10+1=10+20+30+…… +100+1×11+111=（10+100）×10/2+122=672
sorry

What's the law

1=1*1
6=2*3
21=3*7
46=2*23
31=1*31
111=3*37
91=7*13
It is not difficult to find that these numbers are obtained by multiplying 1 or prime numbers. It is suggested to consider them