Simple calculation of 0.8 × 33 × 1.25

Simple calculation of 0.8 × 33 × 1.25

0.8×33×1.25
=0.8×1.25×33
=1×33
=33

30*29-29*28+28*27-27*26+… +4*3-3*2

30*29-29*28+28*27-27*26+… +4*3-3*2
=(30*29-29*28) + (28 * 27-27*26) + .+ ((4*3-3*2)
=29*2 + 27*2 + 25*2 + .+ 3*2
=2* (29+27+25+...+3)
=2* (3+29) * 14 /2
=32 * 14
=448

30^2-29^2+28^2-27^2+…… +2^2-1^2
The sooner the emergency, the better,

Every two combinations from the front to the back
（30^2-29^2）+（28^2-27^2）+…… +（2^2-1^2)
=(30+29)(30-29)+(28+27)(28-27)+.+(2+1)(2-1)
=59 + 55 +. + 3 using Gauss theorem
=(59+3)*15/2=465

30-29 28-27 ……

30-29 28-27 …… 2-1 how to do it
Hello, a plus sign is missing
30-29+ 28-27 …… 2-1
=1+1+1+.+1
=1x15
=15
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Simple mathematical problems: (41 / 12-10 / 7) - (18 / 7-19 / 12)

(41/12-10/7）-（18/7-19/12）
=41/12-10/7-18/7+19/12
=41/12+19/12-(10/7+18/7)
=60/12-28/7
=5-4
=1

1 / 3 + 1 / 6 + 1 / 10 + 1 / 15 + 1 / 21 + ····· + 1 / 1 + 2 + 3 + ···· + 2004 this is a simple mathematical problem, there is always a very simple method

1 / 3 + 1 / 6 + 1 / 10 + 1 / 15 + 1 / 21 + ····· + 1 / 1 + 2 + 3 + ····· + 2004 is the sum of n * (n + 1) / 21 to N, so 1 / 3 + 1 / 6 + 1 / 10 + 1 / 15 + 1 / 21 + ···· + 1 / 1 + 2 + 3 + ····· + 2004 = 2 * (1 / 2 * 3 + 1 / 3 * 4 + 1 / 4 * 5 + ······· + 1 / 2004

Find the next simple problem of seven: (1 / 1 × 2 × 3) + (1 / 2 × 3 × 4) + (1 / 3 × 4 × 5) +... + (1 / 20 × 21 × 22)

*Indicates a multiplication sign
The original formula = 1 / 2 * (1 / 1 * 2-1 / 2 * 3) + 1 / 2 * (1 / 2 * 3-1 / 3 * 4) + +1/2*(1/20*21-1*21*22)
=1/2*(1/1*2-1/2*3+1/2*3-1/3*4+…… +1/20*21-1*21*22)
=1/2*(1/1*2-1*21*22)
=115/462

A simple problem
1 - (1 / 2-1 / 3)
It's a simple calculation

1-(2/1-3/1）
=1-(6/3-6/2)
=1-6/1
=6/6-6/1
=6/5

0.525/13.125/4x85.85/1.01

0.525/13.125/4x85.85/1.01
=[0.525/(13.125×4)]×(85×1.01)/1.01
=0.525/[13×4+0.125×4)]×85
=0.525/(52+0.5)×85
=0.525/(52.5)×85
=0.01×85
=0.85

Several simple problems 1
Use a simple method to calculate the following questions
1．14/15×8
2．2/25×126
3．35×11/36
4．73×74/75
5．1997/1998×1999

1．14/15×8
=（1－1/15）×8
= 8－8/15
=7 and 7 / 15
2．2/25×126
= 2/25×（125＋1）
= 10＋2/25
=10 and 2 / 25
3．35×11/36
=（36－1）×11/36
= 11－11/36
=10 and 25 / 36
4．73×74/75
= 73×（1－1/75）
= 73－73/75
=72 and 2 / 75
5．1997/1998×1999
= 1997/1998×（1998＋1）
= 1997＋1997/1998
=1997 and 1997 / 1998