Bài 1: Tính theo cách hợp lí.
a) 215 + 9-38) – (-58) + 90 – 85
b) 917 – (417 – 65)
c) 31 – [26 – (2017 + 35)]
d) 54 + (-37 + 10 – 54 + 67)
e) (326 – 43) + (174) – 57)
f) (351 – 875) – (125 – 149)
g) -418 – {-218 – [118 – (-131)] + 2017}
giúp mk đi mn!!!!!!
Giải thích:
Bài 1:
a) 215+(-38) – (-58) + 90 – 85
= 215 – 38 + 58 + 90 – 85
= (215 – 85) + (58 – 38)+90
= 130 +20 +90
= 240.
b) 917 – (417 – 65)
= 917 – 417 – 65
= 500 – 65
= 435.
c) 31 – [26 – (2017 + 35)]
= 31 – (26 – 2017 – 35)
= 31- [(26 – 35) – 2017]
= 31- ( -9 – 2017)
= 31 + 9 + 2017
= 40 + 2017
= 2057.
d) 54 + (-37 + 10 – 54 + 67)
= 54 – 37 + 10 – 54 + 67
= (54 – 54)+(67 – 37)+10
= 30 + 10
= 40.
e) (326 – 43) + (174 – 57)
= 326 – 43 + 174 – 57
= (326 + 174) – (43 + 57)
= 500 – 100
= 400.
f) (351 – 875) – (125 – 149)
= 351 – 875 – 125 + 149
= (351 + 149) – ( 875 + 125 )
= 500 – 1000
= -500.
g) -418 – {-218 – [118 – (-131)] + 2017}
= -418 – [-218 – 118 – 131 + 2017]
= -418 + 218 + 118 + 131 – 2017
= (218 + 118 – 418) + (131 – 2017)
= -82 – 1886
= -1968.
@maibui541@ gửi bạn , chúc bn hc tốt!!!~
Đáp án:
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Giải thích các bước giải:
Bài 1: Tính theo cách hợp lí.
a) 215+(-38) – (-58) + 90 – 85
= 215-38+58+90-85
= ( 215-85)+(58-38)+90
= 130+20+90
= 240
b) 917 – (417 – 65)
= 917-417-65
= 500-65
= 435
c) 31 – [26 – (2017 + 35)]
= 31-(26-2017-35)
= 31-[ (26-35) – 2017]
= 31- ( -9-2017)
= 31+9+2017
= 40+2017
= 2057
d) 54 + (-37 + 10 – 54 + 67)
= 54-37+10-54+67
= ( 54-54 )+( 67-37 )+10
= 30+10
= 40
e) (326 – 43) + 174 – 57
= 326-43+174-57
= ( 326+174) – (43+57)
= 500-100
= 400
f) (351 – 875) – (125 – 149)
= 351-875-125+149
= ( 351+149) – ( 875+125 )
= 500-1000
= -500
g) -418 – {-218 – [118 – (-131)] + 2017}
= -418 – [ -218 – 118 -131+2017]
= -418 + 218+118+131-2017
= ( 218+118-418)+(131-2017)
= -82 – 1886
= -1968
CHO XIN HAY NHẤT Ạ!