Simple algorithm of 10 × 11 × 12 × 13 + 11 =!

Simple algorithm of 10 × 11 × 12 × 13 + 11 =!

（11-1）*11（11+1）*13+11 =（121-1）*11*13+11 =120*13*11+11 =120*（12-1）（12+1）+11 =120*（144-1）+11 =120*143+11 =17160+11 =17171

A simple algorithm of 2 / 3 * 5 + 2 / 5 * 7 + 2 / 7 * 9 + 2 / 9 * 11 + 2 / 11 * 13 + 2 / 13 * 15

2/3*5+2/5*7+2/7*9+2/9*11+2/11*13+2/13*15
=1/3-1/5+1/5-1/7+1/7-1/9+...+1/13-1/15
=1/3-1/15
=4/15

A simple algorithm of 0.1 + 0.3 + 0.5 + 0.7 + 0.9 + 0.11 + 0.13 + 0.15. + 0.97 + 0.99
Search for a simple algorithm
Note: from 0.1 to 0.9, it increases by 0.2, and from 0.11 to 0.99, it increases by 0.02

an=a1+(n-1)d
0.9=0.1+(n-1)0.2
n=5
0.99=0.11+(n'-1)0.02
n'=45
0.1+0.3+0.5+0.7+0.9+0.11+0.13+0.15.+0.97+0.99
=[(0.1+0.9)5/2]+[(0.11+0.99)45/2]
=2.5+24.75
=27.25

It is calculated by simple calculation method: 1 and 7 / 2-13 / 9-13 / 4

1 and 2 of 7-13 of 9-13 of 4
=1 and 2 / 7 - (9 / 13 + 4 / 13)
=1 and 2 / 7-1
=Two out of seven

How convenient? 113+114+115+116+117999+998+998+997+997+999．

（1）113+114+115+116+117=115×5=575；（2）999+998+998+997+997+999=（1000-1）+（1000-2）+（1000-2）+（1000-3）+（1000-3）+（1000-1）=1000×5-（1+2+2+3+3+1）=5000-12=4988．

Calculation: 1000 + 999-998 + 997 + 996-995 + +103+102-101=______ ．

1000+999-998+997+996-995+… +103+102-101，=1001+998+995+… +So the answer is: 165750

36 times 25 times four fifths divided by four
Simple calculation

=(36*25)*(4/5/4)
=900*1/5
=180

864 times 37 times 27

864×37×27=863,136

75 times 27 times 4

75 x 27 x 4 =25 x 3 x27 x4 =(25 x4) x (3 x27) =100x 91 =9100

Short calculation: 29 / 29 and 29 / 30

29÷(29+29/30)=1+30=31