Question

Bài 1. Tính nhanh một cách hợp lí

a) (871 - 28 ) + ( 229 - 72 )

b) ( 689 - 31 ) - ( 269 - 111 )

c) 215 + ( - 38) - ( - 58) + 90 - 85

d) 31 - [ 26 - ( 209 + 35 ) ]

e) ( 1267 - 196 ) - ( 267 + 304 ) 

f) ( 3965 - 2378 ) - ( 437 - 1378 ) - 528

 

 

Answer 1

a) (871 - 28 ) + ( 229 - 72 )

= 871 - 28 + 229 - 72

= (871 + 229) - (28 + 72)

= 1100 + 100 = 1200

b) ( 689 - 31 ) - ( 269 - 111 )

= 689 - 31 - 269 + 111

= (689 + 111) - (31 + 269)

= 800 - 300= 500

c) 215 + ( - 38) - ( - 58) + 90 - 85

= 215 - 38 + 58 + 90 - 85

= (215 - 85) + (58 - 38) + 90

= 130 + 20 + 90 = 240

d) 31 - [ 26 - ( 209 + 35 ) ]

= 31 - 26 + 209 + 35

= (31 + 209) + (35 - 26)

= 240 + 9 = 249

e) ( 1267 - 196 ) - ( 267 + 304 ) 

= 1267 - 196 - 67 - 304

= (1267 - 67) - (196 + 304)

= 1200 - 500 = 700

f) ( 3965 - 2378 ) - ( 437 - 1378 ) - 528

= 3965 - 2378 - 437 + 1378 - 528

= 3965 - (2378 - 1378) - (437 + 528)

= 3965 - 1000 - 965 = 3000 - 1000 = 2000

Chúc em học tốt!!!

Answer 2

a) 

871+299- (72+28)

= 1710 - 100

= 1070

k nhé

Answer 3

b) 

=689- 111- (269+31)

= 578 - 300

= 278

k nhoa

Answer 4

c) 215+(-38)-(-58)+90-85

= 215+ (-38)+58+90-85

= (215 - 85)+[58+(-38)]+90

= 130+20+90

=240

Answer 5

a,1070 nhé

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hok tốt

Answer 6

b,276 nha

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hok tốt