Tính bằng cách thuận tiện nhất :

a) 3254 + 146 + 1698

= ( 3254 + 146 ) + 1698

= 3400 + 1698 

= 5098

b) 467 + 999 + 9533

= ( 467 + 9533 ) + 999

= 10000 + 999

= 10999

c) 789 + 285 + 15

= 789 + ( 285 + 15 )

= 789 + 300

= 1089

Tính bằng cách thuận tiện nhất:

a)3254+146+1698

= (3254+146)+1698

= 3400+1698

= 5098

b)467+999+9533

= 467+9533+999

= (467+9533)+999

= 10999+999

=11998

c)789+285+15

= 789+(285+15)

= 789+300

=1089

Tính bằng cách thuận tiện nhất :

a) 3254 + 146 + 1698

= ( 3254 + 146 ) + 1698

= 3400 + 1698 

= 5098

b) 467 + 999 + 9533

= ( 467 + 9533 ) + 999

= 10000 + 999

= 10999

c) 789 + 285 + 15

= 789 + ( 285 + 15 )

= 789 + 300

= 1089

a, \(\dfrac{90}{37}-\dfrac{38}{25}-\dfrac{8}{25}-\dfrac{4}{25}\)

= \(\dfrac{90}{37}\) - \(\dfrac{38+8+4}{25}\)

= \(\dfrac{90}{37}\) - 2

= \(\dfrac{16}{37}\)

\(\dfrac{24}{29}\) + \(\dfrac{32}{41}\) + \(\dfrac{34}{29}\) + \(\dfrac{50}{41}\)

=(\(\dfrac{24}{29}\) + \(\dfrac{34}{29}\)) + (\(\dfrac{32}{41}\) + \(\dfrac{50}{41}\))

= \(\dfrac{58}{29}\) + \(\dfrac{82}{41}\)

= 2 + 2

= 4

c, \(\dfrac{73}{24}\) - \(\dfrac{22}{29}\) - \(\dfrac{25}{24}\) + \(\dfrac{51}{29}\)

= ( \(\dfrac{73}{24}\) - \(\dfrac{25}{24}\)) +( \(\dfrac{51}{29}\) - \(\dfrac{22}{29}\))

= \(\dfrac{48}{24}\) + \(\dfrac{29}{29}\)

= 2 + 1

= 3

a) 285 + 470 + 115 + 230

= (285 + 115) + (470 + 230)

= 400 + 700

= 1 100

b) 571 +216 + 129 + 124

= (571 + 129) + (216 + 124)

= 700 + 340

= 1 040.

a) (-1) + 2 + (-3) + 4 + .... + (-2009) + 2010

= (-1 + 2) + (-3 + 4) + ..... + (-2009 + 2010)

= -1 + (-1) + (-1) + .... + (-1) 

= -1 . 1005 = -1005

b) 1 + (-2) + (-3) + 4 + 5 + (-6) + (-7) + 8 + ... + 2005 + (-2006) + (-2007) + 2008

= [1 + (-2) + (-3) + 4] + [5 + (-6) + (-7) + 8 ] + ..... + [2005 + (-2006) + (-2007) + 2008]

= 0 + 0 + ...... + 0 = 0

ghe

a) Ta có: \(\left(-1\right)+2+\left(-3\right)+4+...+\left(-2009\right)+2010\)

\(=1+1+...+1\)

=1005

b) Ta có: \(1+\left(-2\right)+\left(-3\right)+4+5+\left(-6\right)+\left(-7\right)+8+...+2005+\left(-2006\right)+\left(-2007\right)+2008\)

\(=\left(1-2-3+4\right)+\left(5-6-7+8\right)+...+\left(2005-2006-2007+2008\right)\)

=0

Tính nhanh:

a) 36.(65-79)+65|35-79|

=36.(-14) + 65.44

=-504 + 2860

=2356

b) 12.(34-86)+34.(86-12)+86.(12-34)-12.(34+86)

= 12.(-52) +34.74+86. (-22) - 12.120

=-624 + 2516 +(-1892) -1440

= 1892 + (-1892) -1440

=0- 1440

=-1440

a) 36 . (-14) + 65 . 44

= -504 + 2860

= 2356

Mình làm cho bạn câu cuối

...(x-3)+(x-2)+(x-1)+0+1+2+...+11=11

VP =11

=> VT=11

Để VT =11 cần có đủ cặp số đối đến (10)=> x-3=-10=> x=-7

`-3/8 - (-3/24 ) = -3/8 -(-1/8) = -3/8 + 1/8 = -2/8 = -1/4`

\(-\dfrac{3}{8}-\left(-\dfrac{3}{24}\right)\)

\(=-\dfrac{3}{8}+\dfrac{3}{24}\)

\(=-\dfrac{9}{24}+\dfrac{3}{24}\)

\(=\dfrac{-9+3}{24}\)

\(=-\dfrac{6}{24}\)

\(=-\dfrac{1}{4}\)

$67\cdot12+67\cdot89-67$

$=67\cdot(12+89-1)$

$=67\cdot(101-1)$

$=67\cdot100$

$=6700$

a) \(3119\cdot121-3119\cdot11\cdot11\)

\(=3119\cdot121-3119\cdot\left(11\cdot11\right)\)

\(=3119\cdot121-3119\cdot121\)

\(=3119\left(121-121\right)\)

\(=0\)

b) \(24\cdot\left(123\cdot87\right)+\left(87\cdot123\right)\cdot76\)

\(=\left(123\cdot87\right)\cdot\left(76+24\right)\)

\(=\left(123\cdot87\right)\cdot100\)

\(=1070100\)