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= ( 2380 + 9 x 480) : 25 - 3500 : 25
= ( 2380 + 4320 - 3500 ) : 25
= 3200 : 25
= 128
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a) \(\frac{2}{3}+\frac{5}{4}=\frac{8}{12}+\frac{15}{12}\)
\(=\frac{8+15}{12}=\frac{23}{12}\)
b) \(\frac{15}{25}+\frac{6}{21}=\frac{3}{5}+\frac{2}{7}\)
\(=\frac{21}{35}+\frac{10}{35}=\frac{31}{35}\)
c) \(\frac{35}{11}-2=\frac{35}{11}-\frac{22}{11}\)
\(=\frac{13}{11}\)
d) \(\frac{68}{17}-3=\frac{68}{17}-\frac{51}{17}\)
\(=1\)
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(72x135+9x28x15):25-3500:25
=(72x135+28x135-3500):25
=((72+28)x135-3500):25
=(13500-3500):25
=10000:25=400
(72x135+9x28x15):25-3500:25
=(72x135+72x28):25-3500:25
=135x(72+28):25-3500:25
=135x100:25-3500:25
=13500:25-3500:25
=(13500-3500):25
=10000:25
=400
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a: =2/3(4/9+5/9)=2/3
d: =15/16(9/5-4/5)=15/16
e: =13/25(5-3-1)=13/25
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a: =17/25(13/19+6/19)=17/25
b: \(=\dfrac{47}{19}\cdot\dfrac{32}{15}-\dfrac{47}{19}\cdot\dfrac{17}{15}=\dfrac{47}{19}\)
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C1:
a. 786 x ( 32 +68)
= 786 x 100
= 78600
b. 2904 x 15 + 2904 x 35
= 43560 + 101640
= 145200
c.436 x 72 - 436 x 42
= 31392 - 18312
= 13080
d.194 x (87-7)
= 194 x 80
=15520
e.3332 : (4x49)
= 3332 : 196
= 17
f. 72 : 9 : 8
= (72 : 9) :8
= 1
g. (15 x 24) : 6
= 360 :6
= 60
m. 25 x(36 :9)
= 25 x 4
= 100
Cách 2:
a.786 x 32 + 786 x 68
= 25152 + 53448
= 78600
b. 2904 x ( 15 + 35)
= 2904 x 50
= 145200
c.436 x (72 -42)
= 436 x 30
= 13080
d.194 x 87 - 194 x7
= 16878 - 1358
= 15520
e. 3332 : (4 x 49)
= 3332 : 4 : 49
= 833 : 49 = 17
f. 72 : 9 :8
= 72 : (9 x8)
= 72 : 72
=1
g. (15 x 24) :6
= 15 x (24 :6)
= 15 x 4
= 60
m. 25 x (36 :9)
= ( 25 x36 ):9
= 900 : 9
=100
![](https://rs.olm.vn/images/avt/0.png?1311)
a) \(\dfrac{3}{35}+\dfrac{7}{20}+\dfrac{32}{35}+\dfrac{13}{20}\)
Áp dụng tính chất giao hoán, kết hợp của phép cộng, ta được:
\(\left(\dfrac{3}{35}+\dfrac{32}{35}\right)+\left(\dfrac{7}{20}+\dfrac{13}{20}\right)\)
\(=1+1\)
\(=2\)
b) \(\dfrac{18\cdot15\cdot56}{42\cdot27\cdot25}=\dfrac{2\cdot3\cdot3\cdot5\cdot3\cdot4\cdot2\cdot7}{2\cdot3\cdot2\cdot2\cdot3\cdot9\cdot5\cdot5}\)
\(=\dfrac{2\cdot2\cdot3\cdot3\cdot3\cdot4\cdot5\cdot7}{2\cdot2\cdot2\cdot3\cdot3\cdot5\cdot5\cdot9}=\dfrac{3\cdot2\cdot2\cdot7}{2\cdot5\cdot9}=\dfrac{42}{45}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\text{Ta có:}\)
\(\frac{8}{15}=\frac{8.5}{15.5}=\frac{40}{75}\)
\(\frac{6}{25}=\frac{6.3}{25.3}=\frac{18}{75}\)
\(\text{Vậy...}\)
(68X75+5X32X150):25-5500:25
=(5100+160X150):25-5500:25
=(5100+24000):25-5500:25
=29100:25-5500:25
=1164-220
=994