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2 . 53 . 27 + 6 . 9 . 87 - 3 . 18 . 40
= 2. 53 . 9 . 3 + 2. 3 .9 .87 - 3 .2 .9 .40
= 54.53+54.87-54.40
=54(53+87-40)
=54. 100=5400
12 . 25 + 29 . 25 + 59 . 25
= 25 . ( 12+29+59)
=25 . 90
=2250
43 . 37 + 93 . 43 + 57 . 61 + 69 . 57
= 43.(37+93)+57(61+69)
=43.130+57.130
=130.(43+57)
=130.100
=13 000
12 . 53 + 53 . 172 - 53
=53(12+172-1)
=53.184
=9752
35 . 54 + 35 . 58 + 65 . 75 + 65 . 45
=35(54+58)+65(75+45)
=35.112+65.120
=3920+7800
=11720
39 . 8 + 70 . 3 + 31 . 8
=8(39+31)+70.3
=8.70+70.3
=70.(8+3)
=70.11
=770
Bài 2: Tính nhanh
a) 29 + 132 + 237 + 868 + 3
= 29+(132+858)+(237+3)
=29+990+240
=1259
1) $(-35)\cdot18+28\cdot35$
$=35\cdot(-18)+28\cdot35$
$=35\cdot(-18+28)$
$=35\cdot10$
$=350$
2) $53\cdot29-47\cdot(-29)$
$=53\cdot29-47\cdot(-1)\cdot29$
$=53\cdot29+47\cdot29$
$=29\cdot(53+47)$
$=29\cdot100$
$=2900$
3) $125\cdot(-24)+24\cdot225$
$=(-125)\cdot24+24\cdot225$
$=24\cdot(-125+225)$
$=24\cdot100$
$=2400$
4) $26\cdot(-121)-121\cdot(-36)$
$=-121\cdot[26+(-36)]$
$=-121\cdot(26-36)$
$=-121\cdot(-10)$
$=121\cdot10$
$=1210$
5) $65\cdot(-25)+25\cdot(-23)$
$=-65\cdot25+25\cdot(-23)$
$=25\cdot(-65-23)$
$=25\cdot(-88)$
$=-2200$
6) $237\cdot(-26)+26\cdot137$
$=-237\cdot26+26\cdot137$
$=26\cdot(-237+137)$
$=26\cdot(-100)$
$=-2600$
7) $30\cdot(-125)+25\cdot30$
$=30\cdot(-125+25)$
$=30\cdot(-100)$
$=-3000$
8) $(-37)\cdot69+(-31)\cdot37$
$=37\cdot(-69)+37\cdot(-31)$
$=37\cdot(-69-31)$
$=37\cdot(-100)$
$=-3700$
9) $31\cdot72-31\cdot70-31\cdot2$
$=31\cdot(72-70-2)$
$=31\cdot(2-2)$
$=31\cdot0$
$=0$
10) $(-12)\cdot47+(-12)\cdot52+(-12)$
$=-12\cdot(47+52+1)$
$=-12\cdot100$
$=-1200$
$\text{#}Toru$
A = 1/25x27 + 1/27x29+1/29x31 + ...+ 1/53x55
2A = 3/25x27+ 3/27x29+...+3/53x55
2A = 1/25-1/27+1/27-1/29+...+1/53-1/55
2A = 1/25-1/55
2A = 6/275
A = 6/275:2=3/275
k mk nha, mk lm vội nên coi lại chút giùm mk xem có đúng k
c) 31 x (29 + 53) - 29 x ( 31 - 53)
= 31.29 + 31.53 - 29.31 - 29.53
= (31.29-29.31) + 53.(31-29)
= 0 + 53.2
= 106
ý a bài 1 ý mn
ai rảnh làm cả cũng ok☺♫, mà chắc ko ai rảnh đou ;-; haiz.
a) \((\dfrac{-1}{2})^{3}:\) I\(-1\dfrac{3}{8}\)I -25% .I\(-6\dfrac{2}{11}\)I . (-2)0
\(\dfrac{-1}{8}\) : \(\dfrac{11}{8}\) - \(\dfrac{1}{4}\) . \(\dfrac{68}{11}.1\)
\(\dfrac{-1}{11}-\dfrac{17}{11}=\dfrac{-18}{11}\)
b) \((\dfrac{-5}{9}:\dfrac{4}{11}+\dfrac{-4}{9}:\dfrac{4}{11}).\dfrac{8}{33}\)
\(\dfrac{11}{4}.(\dfrac{-5}{9}+\dfrac{-4}{9}).\dfrac{8}{33}\)
\(\dfrac{11}{4}.(-1).\dfrac{8}{33}\)
\(\dfrac{-2}{3}\)
c) \(\dfrac{-3}{7}.\dfrac{2}{11}+\dfrac{-3}{7}.\dfrac{9}{11}-1\dfrac{3}{7}\)
\(\dfrac{-3}{7}.(\dfrac{2}{11}+\dfrac{9}{11})-1\dfrac{3}{7}\)
\(\dfrac{-3}{7}.1-\dfrac{10}{7}\)
\(\dfrac{-13}{7}\)
Bạn có thể viết rõ hơn ra được không ạ . Chứ mình nhìn nó ra nhiều trường hợp lắm .
a, 36:{336:[200–(12+8.20)]}
= 36:{336:[200–(12+160)]}
= 36:{336:[200–172]}
= 36:{336:28}
= 36:12 = 3
b, {145–[130–(246–236)]:2}.5
= {145–[130–10:2]}.5
= {145–130}.5
= 20.5 = 100
c, 100:{250:[450–(4. 5 3 – 2 2 .25]}
= 100:{250:[450–400]}
= 100:{250:50}
= 100:5 = 20
d, 798+100:[16–2.( 5 2 –22)]
= 798+100:10
= 798+10 = 808
e, (6954+1525:5+47.19).(29–58.2)
= (6954+1525:5+47.19).0 = 0
f, 2 4 .157– 2 4 .58+16
= 16.(157–58+1) = 1600