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bài này mờ quá 

\(25\cdot9\cdot4\cdot100\div1000\)

\(=\left(25\cdot4\right)\cdot9\cdot100\div1000\)

\(=100\cdot9\cdot100\div1000\)

\(=900\cdot100\div1000\)

\(=\frac{90000}{1000}=90\)

Bài làm

\(25.9.4.100:1000\)

\(=\left(25.4\right).9.100:1000\)

\(=100.9.100:1000\)

\(=900.100:1000\)

\(=90000:1000\)

\(=90\)

Học Tốt !

a.  45 và 60

\(45=3^2.5\)

\(60=2^2.3.5\)

\(ƯCLN\left(45;60\right)=3.5=15\)

\(ƯC\left(45;60\right)=Ư\left(15\right)=\left\{1;3;5;15\right\}\)

b.  36 và 180

\(36=2^2.3^2\)

\(180=2^2.3^2.5\)

\(ƯCLN\left(36;180\right)=2^2.3^2=36\)

\(ƯC\left(36;180\right)=Ư\left(36\right)=\left\{1;2;3;4;6;9;12;18;36\right\}\)

c. 48 ; 72 và 90

\(48=2^4.3\)

\(72=2^3.3^2\)

\(90=2.3^2.5\)

\(ƯCLN\left(48;72;90\right)=2.3=6\)

\(ƯC\left(48;72;90\right)=Ư\left(6\right)=\left\{1;2;3;6\right\}\)

d. 100 ; 90 và 18

\(100=2^2.5^2\)

\(90=2.3^2.5\)

\(18=2.3^2\)

\(ƯCLN\left(100;90;18\right)=2\)

\(ƯC\left(100;90;18\right)=U\left(2\right)=\left\{1;2\right\}\)

e. 16 và 96

\(16=2^4\)

\(96=2^5.3\)

\(ƯCLN\left(16;96\right)=2^4=16\)

\(ƯC\left(16;96\right)=Ư\left(16\right)=\left\{1;2;4;8;16\right\}\)

Học Tốt !

a,45 và 60

\(45=3^2.5\)

\(60=2^2.3.5\)

\(\Rightarrow UCLN\left(45;60\right)=3.5=15\)

\(Ư\left(15\right)=\left\{1;3;5;15\right\}\)

Giải

Thời gian để hai người đi hết đoạn đường là:

3 x 2 = 6 ( giờ )

Trung bình mỗi giờ một người đi được số ki - lô - mét là:

216 : 6 = 36 (km)

                      Đ/S:

1.I saw/ have seen that flim aready 

2 we went / have gone to the movies three times last month

3 did you ever do / have you ever done volunteer work ?

4 i had / have had five tests so far this semester 

5 linda did / has done her homework before she went to sleep

6 she bought / has bought a neww mobile phone two days ago

1.I saw/ have seen that flim aready 

2 we went / have gone to the movies three times last month

3 did you ever do / have you ever done volunteer work ?

4 i had / have had five tests so far this semester 

5 linda did / has done her homework before she went to sleep

6 she bought / has bought a neww mobile phone two days ago