bài 2 : tính hợp lí
a)29,42+20,58-34,23+(-25,77)
b) (-212,49)-(87,51-99,9)
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NA
3
11 tháng 5 2021
a) 29,42 + 20,58 - 34,23 + (-25,77)
=(29,42+20,58)+(-34,23+-25,77)
=50+-60
=-10
b) (-212,49) - (87,51 - 99,9)
=-212,49-87,51+99,9
=(-212,49-87,51)+99,9
=-300+99,9
=-200,1
11 tháng 5 2021
`a) 29,42 + 20,58 - 34,23 + (-25,77)`
`=29+0,42+20+0,58-34-0,23-25-0,77`
`=29+20-34-25+0,42+0,58-(0,23+0,77)`
`=49-59+1-1`
`=-10`
`b) (-212,49) - (87,51 - 99,9).`
`=-212,49-87,51+99,9`
`=-(212,49+87,51)+99,99=`
`=-299,9+99,9`
`=-200`
NH
22 tháng 2 2023
`(-225,65)-(87,51-99,9)`
`=-225,65-87,51+99,99`
`=-313,16+99,9`
`=-213,26`
H2
1
NP
1
7 tháng 7 2023
`@` `\text {Ans}`
`\downarrow`
`1,`
`a)`
`5 \times 72 \times 10 \times 2`
`= 5 \times 2 \times 10 \times 72`
`= 10 \times 10 \times 72`
`= 100 \times 72`
`= 7200`
`b)`
`40 \times 125`
`= 4 \times 10 \times 25 \times 5`
`= (5 \times 10) \times (4 \times 25)`
`= 50 \times 100`
`= 5000`
`c)`
`4 \times 2021 \times 25`
`= (4 \times 25) \times 2021`
`= 100 \times 2021`
`= 202100`
`d)`
`16 \times 6 \times 25`
`= 4 \times 4 \times 6 \times 25`
`= (4 \times 25) \times 4 \times 6`
`= 100 \times 24`
`= 2400`
`2,`
`a)`
`24 \times 57 + 43 \times 24`
`= 24 \times (57+43)`
`= 24 \times 100`
`= 2400`
`b)`
`12 \times 19 + 80 \times 12 +12`
`= 12 \times (19 + 80 + 1)`
`= 12 \times 100`
`= 1200`
`c)`
`(36 \times 15 \times 169) \div (5 \times 18 \times 13)`
`= 36 \times 15 \times 169 \div 5 \div 18 \div 13`
`= 6 \times 6 \times 3 \times 5 \times 13 \times 13 \div 5 \div 3 \times 6 \div 13`
`= (6 \div 6) \times (3 \div 3) \times (5 \div 5) \times (13 \div 13) \times 6 \times 13`
`= 6 \times 13`
`= 78`
`d)`
`(44 \times 52 \times 60) \div ( 11 \times 13 \times 15)`
`= 44 \times 52 \times 60 \div 11 \div 13 \div 15`
`= 4 \times 11 \times 13 \times 4 \times 15 \times 4 \div 11 \div 13 \div 15`
`= (11 \div 11) \times (13 \div 13) \times (15 \div 15) \times 4 \times 4 \times`
`= 4 \times 4 \times 4`
`= 64`
`3,`
`a)`
`x - 280 \div 35 = 5 \times 54`
`x - 8 = 270`
`x = 270 + 8`
`x = 278`
`b)`
`(x - 280) \div 35 = 54 \div 4`
`(x - 280) \div 35 = 13,5`
`x - 280 = 13,5 \times 35`
`x - 280 = 472,5`
`x = 472,5 + 280`
`x = 752,5`
`c)`
`(x - 128 + 20) \div 192 = 0`
`x - 128 + 20 = 0 \times 192`
`x - 128 + 20 = 0`
`x - 108 = 0`
`x = 0 + 108`
`x = 108`
`d)`
`4 \times (x + 200) = 460 + 85 \times 4`
`4 \times (x+200) = 460 + 340`
`4 \times (x+200) = 800`
`x + 200 = 800 \div 4`
`x + 200 = 200`
`x = 200 - 200`
`x = 0`
`4,`
`a)`
`7/12 - 5/12`
`= (7 - 5)/12`
`= 2/12`
`= 1/6`
`b)`
`8/11 + 19/11`
`= (8+19)/11`
`= 27/11`
`c)`
`3/8 + 5/12`
`= 9/24 + 10/24`
`= 19/24`
`d)`
`3/4 + 7/12`
`= 9/12 + 7/12`
`= 16/12`
`= 4/3`
`5,`
`a)`
`x - 6/7 = 5/2`
`x = 5/2 + 6/7`
`x = 47/14`
`b)`
`12/7 \div x + 2/3 = 7/5`
`12/7 \div x = 7/5 - 2/3`
`12/7 \div x = 11/15`
`x = 12/7 \div 11/15`
`x = 180/77`
`@` `\text {Kaizuu lv uuu}`
6 tháng 1 2022
a: =-64(32+68)=64x100=-6400
b: =76(-54-12+36)=76x(-30)=-2380
c: =19x50+38x5=950+190=1140
BF
10 tháng 2 2023
`1 - 2 + 3 - 4 + 5 - 6 +...+ 2021 - 2022`
`= (1 - 2) + (3 - 4) + (5 - 6) +...+ (2021 - 2022)`
`= (-1) + (-1) + (-1) + ... + (-1) ` [có `2022 : 2 = 1011` nhóm]
`= (-1) xx 1011 = -1011`
HB
2
31 tháng 10 2021
a, \(\dfrac{3}{5}.\left(-\dfrac{8}{3}\right)-\dfrac{3}{5}:\left(-\dfrac{3}{2}\right)=\dfrac{3}{5}.\left(-\dfrac{8}{3}\right)-\dfrac{3}{5}.\left(-\dfrac{2}{3}\right)==\dfrac{3}{5}\left(-\dfrac{8}{3}-\dfrac{2}{3}\right)=\dfrac{3}{5}.\left(-\dfrac{10}{3}\right)=-2\)
b, \(-\dfrac{5}{6}.\left(-\dfrac{12}{7}\right)-\left(-\dfrac{21}{15}\right)=-\dfrac{5}{6}.\left(-\dfrac{12}{7}\right)+\dfrac{7}{5}=\dfrac{10}{7}+\dfrac{7}{5}=\dfrac{50+49}{35}=\dfrac{99}{35}\)
31 tháng 10 2021
a: \(=\dfrac{3}{5}\cdot\left(-\dfrac{8}{3}+\dfrac{-2}{3}\right)=\dfrac{3}{5}\cdot\dfrac{-10}{3}=-2\)
c: \(=\left(0.125\right)^{650}\cdot8^{102}\)
\(=\left(0.125\cdot8\right)^{102}\cdot\left(0.125\right)^{548}\)
\(=\dfrac{1}{8^{548}}\)
a) \(\left(29,42+20,58\right)-\left(34,23+25,77\right)\)
\(=50-60=-10\)
b) \(-\left(212,49+87,51\right)+99,9\)
\(=-300+99,9=-200,1\)
A)29.42+20.58−34.23+(−25.77)29.42+20.58−34.23+(−25.77)
=29.42+20.58−34.23−25.77
=29.42+20.58−34.23−25.77
=(29.42+20.58)−(34.23+25.77)
=(29.42+20.58)−(34.23+25.77)
=50−60=50−60
=−10=−10
B).(−212.49)−(87.51−99.9)(−212.49)−(87.51−99.9)
=−212.49−87.51+99.9
=−212.49−87.51+99.9
=−(212.49+87.51)+99.9
=−(212.49+87.51)+99.9
=−300+99.9=−300+99.9
=−(300−99.9)=−(300−99.9)
=−200.1