\(\dfrac{1}{2}\) + \(\dfrac{1}{6}\) + \(\dfrac{1}{12}\) + \(\dfrac{1}{20}\) + \(\dfrac{1}{30}\)

=\(\dfrac{1}{1.2}\) + \(\dfrac{1}{2.3}\) + \(\dfrac{1}{3.4}\) + \(\dfrac{1}{4.5}\) + \(\dfrac{1}{5.6}\)

=\(\dfrac{1}{1}\) - \(\dfrac{1}{2}\) + \(\dfrac{1}{2}\) - \(\dfrac{1}{3}\) + \(\dfrac{1}{3}\) - \(\dfrac{1}{4}\) + \(\dfrac{1}{4}\) -\(\dfrac{1}{5}\) +\(\dfrac{1}{5}\) - \(\dfrac{1}{6}\)

=\(\dfrac{1}{1}\) - \(\dfrac{1}{6}\)

=\(\dfrac{5}{6}\)

  10 . 2 + 10 . 3                                                                     4 . 3 + 2 . 4

=10 . (2 + 3)                                                                      =4 . (3 + 2)

=10 . 5                                                                               =4 . 5

=50                                                                                    =20

a, x - 10 + 20=25 + 35

x -10 + 20=60

x - 10=60 - 20

x - 10=40

x=40 + 10

x=50

b, x - 15 + 25=70 - 20

x - 15 + 25=50

x - 15=50 - 25

x - 15=25

x=25 + 15

x=40

4+2+3+200+200+300+12345

=9+400+300+12345

=9+700+12345

=709+12345

=13054

10000+20000+2543+125444

=30000+2543+125444

=32543+125444

=157987

Đao Trong Luan was wrong

1 + 2 + 3 + 10000000

=6+10000000

=10000006

12 apples respectively:

1 - \(\dfrac{1}{2}\)=\(\dfrac{1}{2}\) of the numbers of apples Anna has

Anna has: 12 :  \(\dfrac{1}{2}\)=24(apples)

Answer:24 apples

\(\dfrac{3}{5}\) + \(\dfrac{3}{2}\) + \(\dfrac{1}{5}\) + \(\dfrac{1}{2}\)

=(\(\dfrac{3}{5}\) + \(\dfrac{1}{5}\)) + (\(\dfrac{3}{2}\) + \(\dfrac{1}{2}\))

=\(\dfrac{4}{5}\) + \(\dfrac{4}{2}\)

=\(\dfrac{4}{5}\) + 2

=\(\dfrac{14}{5}\)

100 + 200 + 300 + 400+500+600+700+800+900

=(1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9) . 100

=45 . 100

=4500

a, x-10=10+20

x-10=30

x=30+10

x=40

b, 10+x=20+30

10+x=50

x=50-10

x=40

100+200+300+400+500+600+700+800+900

=(100+900)+(200+800)+(300+700)+(400+600)+500

=1000+1000+1000+1000+500

=1000 . 4+500

=4000+500

=4500

6 chair  can accommodate the number of people are:

72 - 36=36(people)

1 chair  can accommodate the number of people are:

36 : 6=6(people)

3 chair  can accommodate the number of people are:

6 . 3=18(people)

Answer: 18 people

E(It is impossible)

Mình mong các bạn khắc các lỗi mà Lê Quốc Trần Anh đưa ra

6 người nữa là ai vậy bạn:

Edge of the square:

48 : 4=12 (cm)

The rectangle length is:

12 . 2=24(cm)

Rectangle width is:

12 : 2=6(cm)

The circumference of the rectangle is:

(24+6) . 2=60(cm)

    Answer:60 cm

102

103

104

-----

309

A=0

The number of minutes to cut a log into 1 piece is:

30 : 6=5(minutes)

The numbers of minutes to cut a log into 9 piece is:

5 . 9=45(minutes)

5 digit  numbers have 5 digits

4 digit numbers have 4 digits

And numbers are 5 digits larger than 4 digits