How to calculate the law of half plus one sixth + one twelfth + one twentieth, one thirtieth + one forty second

How to calculate the law of half plus one sixth + one twelfth + one twentieth, one thirtieth + one forty second

1 / 2 + 1 / 6 + 1 / 12 + 1 / 20 + 1 / 30 + 1 / 42
=(1-1/2)+(1/2-1/3)+(1/3-1/4)+(1/4-1/5)+(1/5-1/6)+(1/6-1/7)
=1-1/7=6/7

Half + one sixth + one twelfth + one twentieth + ·····················································································
Urgency. Homework. Famous teacher. Urgency: * * **

1/2+1/6+1/12+1/20+.+1/9900
=（1-1/2）+（1/2-1/3）+（1/3-1/4）+（1/4-1/5）+...+（1/99-1/100）
=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+...+1/99-1/100
=1-1/100
=99/100

Two thirds minus (two seventh plus one sixth) is calculated by the formula

2/3-（2/7+1/6）
=2/3-2/7-1/6
=28/42-12/42-7/42
=12/42-7/42
=5/42

2 / 3 minus 6 / 5 plus 1 / 3

2/3-5/6+1/3=（2/3+1/3）-5/6=1/6

Minus four and six minus three and five minus three and six minus one and five

Negative 12 and 4 / 5

Minus one fifth minus five Sixth

-31/30

Fill in the blanks: two fifths of 1.6km is equal to one sixth of () km?
The previous question is not 1.6, but 6 kilometers

1. Two fifths of 6 km is equal to one sixth of (72 / 5) km
2. (1): (20) = 0.05 = 2 ÷ (40) = 4 / 80

(0.81 × 0.75 × 0.48) / (0.25 × 0.24 × 0.27)

(0.81×0.75×0.48)÷(0.25×0.24×0.27)
=(0.27×3×0.25×3×0.24×2)÷(0.25×0.24×0.27)
=3×3×2
=18

How to calculate 22 * 0.75 + 25 * 75-7 * 0.75

22 * 0.75 + 25 * 75-7 * 0.75
=0.75*(22+25-7)
=0.75*40
=30

Simple calculation: four fifths - four fifths △ two thirds × one half =?

Four fifths - four fifths △ two thirds × one half
=Four fifths - four fifths × three fifths × one half
=Four fifths - four fifths x three fourths
=Four fifths × (1-three fourths)
=Four fifths by one fourth
=One in five