The weight of the largest piece is:

900 : 2=450(g)

a, 100 . 10 + 200 . 10

=10 . (100 + 200)

=10 . 300

=3000

b, 10 . 20 + 20 . 40

=20 . (10+40)

=20 . 50

=1000

123,45 + 23,56 + 76,44 + 54,55

=(123,45 + 54,55) + (23,56 + 76,44)

=178 + 100

=278

237+2456+1763+544

=(237+1763)+(2456+544)

=2000+3000

=5000

Human. You should write in english

We see that:

\(\dfrac{1}{3.6}\)=\(\dfrac{1}{3}\). \(\dfrac{3}{3.6}\)=\(\dfrac{1}{3}\). \(\dfrac{1}{3}\)- \(\dfrac{1}{6}\)

=>A=\(\dfrac{1}{3}\). \(\dfrac{1}{3}\)- \(\dfrac{1}{6}\)+ \(\dfrac{1}{6}\)- \(\dfrac{1}{9}\)+...+\(\dfrac{1}{123}\)- \(\dfrac{1}{126}\)

       =\(\dfrac{1}{3}\). \(\dfrac{1}{3}\)- \(\dfrac{1}{126}\)

       =\(\dfrac{41}{378}\)

a , 50+100+10+50+900

=(50+50)+(100+900)+10

=100+1000+10

=1100+10

=1110

b ,30+80+40+70+60+20

=(30+70)+(80+20)+(40+60)

=100+100+100

=100 . 3

=300

c ,20+50+40+30+10

=(20+30+40+10)+50

=100+50

=150

Tom has euro is:

100. 9+ 10. 9+ 1. 10=1000(euro)

The smallest positive integer divisible by 2,3 and 4 is:

LCM(2;3;4)=2². 3=4. 3=12 

We see that:

\(\dfrac{1}{5.9}\)=\(\dfrac{1}{4}\). \(\dfrac{4}{5.9}\)=\(\dfrac{1}{4}\). \(\dfrac{1}{5}\)- \(\dfrac{1}{9}\)

=>A=\(\dfrac{1}{4}\). \(\dfrac{1}{5}\)- \(\dfrac{1}{9}\)+ \(\dfrac{1}{9}\)- \(\dfrac{1}{13}\)+...+\(\dfrac{1}{161}\)- \(\dfrac{1}{165}\)

       =\(\dfrac{1}{4}\). \(\dfrac{1}{5}\)- \(\dfrac{1}{165}\)

       =\(\dfrac{8}{165}\)

3^2+3^3+3^4

=9+27+81

=36+81

=117

Bùi Thị Vân is that right

Ok

50+70+90+30+10

=(70+30)+(10+90)+50

=100+100+50

=200+50

=250

1000+250+900+300+700+100+750

=(250+750)+(900+100)+(300+700)+1000

=1000+1000+1000+1000

=1000. 4

=4000

We see that:

\(\dfrac{1}{3.6}\)=\(\dfrac{1}{3}\). \(\dfrac{3}{3.6}\)=\(\dfrac{1}{3}\). \(\dfrac{1}{3}\)- \(\dfrac{1}{6}\)

=>A=\(\dfrac{1}{3}\). \(\dfrac{1}{3}\)- \(\dfrac{1}{6}\)+ \(\dfrac{1}{6}\)- \(\dfrac{1}{9}\)+...+\(\dfrac{1}{132}\)- \(\dfrac{1}{135}\)

       =\(\dfrac{1}{3}\). \(\dfrac{1}{3}\)- \(\dfrac{1}{135}\)

       =\(\dfrac{44}{405}\)

   (900-38). 38+ (800+ 62). 62

=(800+ 100- 38). 38+ (800+ 62). 62

=(800+ 62). 38+ (800+ 62). 62

=(800+ 62)+[38+ 62]

=862. 100

=86200

\(\dfrac{50}{309}\)is wrong

Lê Quốc Trần Anh is was wrong

We see that: \(\dfrac{1}{6.10}\)=\(\dfrac{1}{4}\). \(\dfrac{4}{6.10}\)=\(\dfrac{1}{4}\).  \(\dfrac{1}{6}\)- \(\dfrac{1}{10}\)

=>A=\(\dfrac{1}{4}\).  \(\dfrac{1}{6}\)- \(\dfrac{1}{10}\)+ \(\dfrac{1}{10}\)- \(\dfrac{1}{14}\)+...+\(\dfrac{1}{202}\)- \(\dfrac{1}{206}\)

       =\(\dfrac{1}{4}\). \(\dfrac{1}{6}\)- \(\dfrac{1}{206}\)

       =\(\dfrac{25}{618}\)

With No Big = 12 x số bé

Should be number: number be = 12

The hand of the number of 12

With a number of 12: 2 = 6

With Số lớn bằng: 12 x 6 = 72

   20+30+40+50+60+70

=(30+70)+(40+60)+(20+50)

=100+100+70

=100.2+70

=200+70

=270