Bài toán 9 : Tính hợp lý.
a. 4567 + (1234 – 4567) -4
k. (-18) + (-31) + 98 + |-18| + (-69)
b. 2001 – (53 + 1579) – (-53)
l. 17. (15 – 16) + 16.(17 – 20)
c. 35 – 17 + 2017 – 35 + (-2017)
m. 15.(-176) + 15.76 + 100.15
d. 37 + (-17) – 37 + 77
n. 79.89 – 79.(-11) – 100.79
e. –(-219) + (-219) – 401 + 12
o. 153.177 – 153.77 + 100.(-77)
f. |-85| – (-3).15
p. -69.|-45| – 31.|45|
g. 11.107 + 11.18 – 25.11
q. (-29).(85 – 47) – 85.(47 – 29)
h. 115 – (-85) + 53 – (-500 + 53)
r. (-167).(67 – 34) – 67.(34 – 167)
Giải thích các bước giải:
a) 4567 + (1234 – 4567) -4
= 4567 + 1234 – 4567 – 4
= (4567 – 4567) + (1234 – 4)
= 0 + 1230
= 1230
b) 2001 – (53 + 1579) – (-53)
= 2001 – 53 – 1579 + 53
= (2001 – 1579) + [(-53) + 53]
= 422 + 0
= 422
c) 35 – 17 + 2017 – 35 + (-2017)
= 35 – 17 + 2017 – 35 – 2017
= (35 – 35) + (2017 – 2017) – 17
= 0 + 0 – 17
= -17
d) 37 + (-17) – 37 + 77
= 37 – 17 – 37 + 77
= (37 – 37) + [(-17) + 77]
= 0 + 60
= 60
e) –(-219) + (-219) – 401 + 12
= 219 – 219 – 401 + 12
= (219 – 219) + [(-401) + 12]
= 0 + (-389)
= – 389
f) |-85| – (-3).15
= 85 + 3 . 15
= 85 + 45
= 130
g)11.107 + 11.18 – 25.11
= 11 . ( 107 + 18 – 25)
= 11 . ( 125 – 25)
= 11 . 100
= 1100
h) 115 – (-85) + 53 – (-500 + 53)
= 115 + 85 + 53 + 500 – 53
= (115+ 85) + (53 – 53) + 500
= 200 + 0 + 500
= 700
k) (-18) + (-31) + 98 + |-18| + (-69)
= – 18 – 31 + 98 + 18 – 69
= [(-18) + 18] + [(-31) + (-69)] + 98
= 0 + (-100) + 98
= -100 + 98
= -2
= 17 . 15 – 16 + 16 . 17 – 20
= 17 . (15 – 20) + [(-16) + 16]
= 17 . (-5) + 0
= -85
l) 15.(-176) + 15.76 + 100.15
= 15 . [(-176) + 76 + 100]
= 15 . [-100 + 100]
= 15 . 0
= 0
m) 79.89 – 79.(-11) – 100.79
= 79 . [89 – (-11) – 100]
= 79 . [89 + 11 – 100]
= 79 . [100 – 100]
= 79 . 0
= 0
n) 153.177 – 153.77 + 100.(-77)
= 153 . ( 177 – 77) + 100 . (-77)
= 153 . 100 + 100 . -77
= 100 . (153 – 77)
= 100 . 76
= 7600
p) -69.|-45| – 31.|45|
= – 69 . 45 – 31 . 45
= 45 . [-(69 + 31)]
= 45 . 100
= 4500
a)
= `4567 + 1234 – 4567 – 4`
=` (4567 – 4567) + (1234 – 4)`
= `0 + 1230`
= `1230`
b)
= `2001 – 53 – 1579 + 53`
= `(2001 – 1579) + [(-53) + 53]`
= `422 + 0`
= `422`
c)
= `35 – 17 + 2017 – 35 – 2017`
= `(35 – 35) + (2017 – 2017) – 17`
= `0 + 0 – 17`
= `-17`
d)
= `37 – 17 – 37 + 77`
= `(37 – 37) + [(-17) + 77]`
= `0 + 60`
= `60 `
e)
= `219 – 219 – 401 + 12`
= `(219 – 219) + [(-401) + 12]`
= `0 + (-389)`
= `- 389`
f)
= `85 + 3 . 15`
= `85 + 45`
= `130`
g)
= `11 . ( 107 + 18 – 25)`
= `11 . ( 125 – 25)`
= `11 . 100`
= `1100`
h) `115 – (-85) + 53 – (-500 + 53)`
= `115 + 85 + 53 + 500 – 53`
= `(115+ 85) + (53 – 53) + 500`
= `200 + 0 + 500`
= `700`
k)
= `- 18 – 31 + 98 + 18 – 69`
= `[(-18) + 18] + [(-31) + (-69)] + 98`
= `0 + (-100) + 98`
= `-100 + 98`
= `-2`
= `17 . 15 – 16 + 16 . 17 – 20`
= `17 . (15 – 20) + [(-16) + 16]`
= `17 . (-5) + 0`
= `-85`
l)
= `15 . [(-176) + 76 + 100]`
= `15 . [-100 + 100]`
= `15 . 0`
= `0`
m)
= `79 . [89 – (-11) – 100]`
= `79 . [89 + 11 – 100]`
= `79 . [100 – 100]`
= `79 . 0`
= `0`
n)
= `153 . ( 177 – 77) + 100 . (-77)`
= `153 . 100 + 100 . -77`
= `100 . (153 – 77)`
= `100 . 76`
= `7600`
p) = `- 69 . 45 – 31 . 45`
= `45 . [-(69 + 31)]`
= `45 . 100`
= `4500`