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1.8100
2. 34 x 18 + 18 x 66
= 18 x ( 34 + 66)
= 18 x 100 = 1800
3. X × ( 8 + 12) = 160 + 20 × 12
= X x 20 = 160 + 240
= X x 20 = 400
X = 400 : 20 = 20
4. X x 12 - X x 2 = 2020
(12 - 2) x X = 2020
10 x X = 2020
X = 2020 : 10 = 202
a, 32684 + 41325 + 316 + 675
= (32684 + 316) + (41325 + 675)
= 33 000 + 42 000
= 75 000
b, 25 \(\times\) 18 \(\times\) 4 \(\times\) 2
= (25 \(\times\) 4) \(\times\) (18 \(\times\) 2)
= 100 \(\times\) 36
= 3600
49 x 37 = 37 x 49
(214 x 25) x 4 = 214 x (25 x 4)
103 x 18 + 103 x 12 = 103 x (18 + 12)
a: \(=\dfrac{18}{51}\cdot\dfrac{34}{9}\cdot\dfrac{17}{18}=\dfrac{17}{51}\cdot\dfrac{34}{9}=\dfrac{1}{3}\cdot\dfrac{34}{9}=\dfrac{34}{27}\)
b: \(=\dfrac{21}{32}\cdot\dfrac{4}{7}\cdot25\cdot\dfrac{4}{5}=\dfrac{21}{7}\cdot\dfrac{4}{32}\cdot20=60\cdot\dfrac{1}{8}=\dfrac{15}{2}\)
Bài 2: Tính bằng cách thuận tiện nhất
\(\text{a. 1255 + 436 + 145}\)
\(=\left(1255+145\right)+436\)
\(=1400+436\)
\(=1836\)
\(\text{b. 142 x 12 + 142 x 18}\)
\(=142\times\left(12+18\right)\)
\(=142\times30\)
\(=4260\)
\(\text{c. 4 x 18 x 25}\)
\(=\left(25\times4\right)\times18\)
\(=100\times18\)
\(=1800\)
Bài 2:
a: \(=1400+436=1836\)
b: =142(12+18)
=142*30
=4260
c: \(=100\cdot18=1800\)
Bài 3:
a: \(41m^219dm^2>409dm^2\)
b: \(90000cm^2< 90m^2\)
c: \(30m^26dm^2< 3060dm^2\)
d: \(8012cm^2>8dm^212cm^2\)
e: \(5dm^29cm^2=509cm^2\)
f: \(3940dm^2=39m^240dm^2\)
g: \(300m^26dm^2>3006dm^2\)
h: \(2009cm^2< 21dm^2\)
a: \(32684+41325+316+675\)
\(=\left(32684+316\right)+\left(41325+675\right)\)
\(=33000+42000=75000\)
b: \(25\cdot18\cdot4\cdot2\)
\(=18\cdot2\cdot\left(25\cdot4\right)\)
\(=36\cdot100=3600\)
c: \(19\cdot81+19+18\cdot19\)
\(=19\left(81+1+18\right)\)
\(=19\cdot100=1900\)
A, 32684 + 41325 + 316 + 675
=(32684+316)+(41325+675)
=33000+42000
=75000
B, 25 x 18 x 4 x 2
=(25x4)x(18x2)
=100x36
=3600
C, 19 x 81 + 19 + 18 x 19
=19x(81+18+1)
=19x100
=1900
a) 142 x 12 + 42 x 18
= 142 x (12 +18)
= 142 x 30 = 4260
b) 49 x 365 - 39 x 365
= (49-39) x 365
= 10 x 365 = 3650
c) 4 x 18 x 25
= 18 x (4 x 25)
= 10 x 100 = 1800
3600
3600