Bài 1 tự làm :v Làm ở đây ngốn nhiều time :))

2. Số bé là : ( 250 - 12 ) : 2 = 119

Số lớn là : 250 - 119 = 131

3. Nửa chu vi thửa ruộng : 480 : 2 = 240m

Chiều dài thửa ruộng : 240 : ( 5 + 3 ) . 5 = 150m

Chiều rộng thửa ruộng : 240 - 150 = 90m

Diện tích thửa ruộng : 150 . 90 = 13 500m²

bn ơi lm bài 1 hộ mk với

a) 1 + 3 + 5 + 7 + 9 + 11 + 13 + 15 + 17 + 19

= (1 + 19) + (3 + 17) + (5 + 15) + (7 + 13) + (9 + 11)

= 20 + 20 + 20 + 20 + 20

= 100

b) 15 × 25 + 25 × 34 + 51 × 25

= 25 × (15 + 34 + 51)

= 25 × 100

= 2500

File: undefined 

415441

30 273 + 2918 = 33 191

98 234 - 32 508 = 65 726

29 251 x 3 = 87 753

14 286 : 7 = 2040(dư 6)

= 625 nha em

HT

25x25=625

nha bn Quỳnh Như

1) 1/2*1/6=1/12 ; 1/3*1/4=1/12. Ta có : 17/5+1/12*71/5-1/12*28/5=1/12*(17/5+71/5-28/5)=1/12*60/5=1/12*12=1      2)1/10+4/20+9/30+16/40+25/50                   =1/10+2/10+3/10+4/10+5/10(rút gọn)            =15/10=3/2                                               3)18/15*(2525/3636+1515/1818-2020/7272)=6/5*(25/36+5/6-5/18)(rút gọn)=6/5*25/36+6/5*5/6-6/5*5/18=5/6+1-1/3=9/6=3/2.

1.

  \(\frac{5}{3}-\frac{1}{4}+\frac{1}{3}-\frac{3}{4}\)

\(=\left(\frac{5}{3}+\frac{1}{3}\right)-\left(\frac{1}{4}+\frac{3}{4}\right)\)

\(=2-1=1\)

\(\frac{2}{7}\cdot\frac{1}{5}+\frac{2}{7}\cdot\frac{4}{5}=\frac{2}{7}\cdot\left(\frac{1}{5}+\frac{4}{5}\right)=\frac{2}{7}\cdot1=\frac{2}{7}\)

                               #Louis

\(1.a)\frac{5}{3}-\frac{1}{4}+\frac{1}{3}-\frac{3}{4}\)

\(=\left(\frac{5}{3}+\frac{1}{3}\right)-\left(\frac{1}{4}+\frac{3}{4}\right)\)

\(=2-1\)

\(=1\)

\(b)\frac{2}{7}\times\frac{1}{5}+\frac{2}{7}\times\frac{4}{5}\)

\(=\frac{2}{7}\times\left(\frac{1}{5}+\frac{4}{5}\right)\)

\(=\frac{2}{7}\times1\)

\(=\frac{2}{7}\)

\(2.a)\frac{5}{6}+\frac{7}{12}-\frac{2}{9}\)

\(=\frac{30}{36}+\frac{21}{36}-\frac{8}{36}\)

\(=\frac{43}{36}\)

\(b)\frac{4}{9}\times\frac{5}{8}+\frac{1}{6}\)

\(=\frac{5}{18}+\frac{1}{6}=\frac{5}{18}+\frac{3}{18}\)

\(=\frac{8}{18}=\frac{4}{9}\)

\(c)2:\frac{3}{11}-\frac{13}{12}\)

\(=2\times\frac{11}{3}-\frac{13}{12}\)

\(=\frac{22}{3}-\frac{13}{12}\)

\(=\frac{25}{4}\)

a ( 1+2+3+4+....+99)*(13*15-12*25-15)
= ( 1+2+3+4+....+99)*[15*(13-1)-12*25)]
=( 1+2+3+4+....+99)*[15*12-12*25]
=( 1+2+3+4+....+99)*[12*(15-25)]
=( 1+2+3+4+....+99)*[12*(-10)]
=( 1+2+3+4+....+99)*(-120)
= -594000
b 3*5*36+15+42+30*11
=15*36+15*1+42+15*22
=15*(36+1+22)+42
=15*59+42
=885+42
=927
Tick cho mk nha
 

a. ( 1+2+3+4+....+99)*(13*15-12*25-15)

=( 1+2+3+4+....+99) . 0

=0

 b 3*5*36+15+42+30*11

=540 + 15 +42 + 330

=927