47-[(45.24-52.12):14
50-[(20-23):2+34]
102-[60:(56;54-3.5
TRINH BAY CACH GIAI GIUM MINH
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a, 75 + 58.50 – 58.25 = 3.25 + 58.(50 – 25) = 3.25 + 58.25 = 25.(3+58) = 25.61 = 1525
Ta có: 1525 = 5 2 . 61
b, 20: 2 2 – 5 9 : 5 8 = 20:4 – 5 = 5 – 5 = 0
c, 5 19 : 5 17 - 4 : 7 = 5 2 - 4 : 7 = (25 – 4):7 = 3
d, 47 - 45 . 2 4 - 5 2 . 12 : 14 = 47 – (45.16 – 25.12):14 = 47 – (720 – 300):14 = 47 – 420:14 = 47 – 30 = 17
e, 10 2 : 60 : 5 6 : 5 4 - 3 . 5 = 100 – 60: 5 2 - 15 = 100 – 60:(25 – 15) = 100 – 60:10 = 100 – 6 = 94
Ta có: 94 = 2.47
f, 2345 - 1000 : 19 - 2 21 - 18 2 = 2345 – 1000:(19 – 2. 3 2 ) = 2345 – 1000:(19 – 2.9) = 2345 – 1000:(19 – 18) = 2345 – 1000:1 = 2345 – 1000 = 1345
Ta có: 1345 = 3.269
g, 500 – {5.[409 – 2 3 . 3 - 21 2 ]+ 10 3 }:15 = 500 – {5.[409 – 8 . 3 - 21 2 ]+1000}:15 = 500 – {5.[409 – 3 2 ]+1000}:15 = 500 – {5.(409 – 9)+1000}:15 = 500 – {5.400+1000}:15 = 500 – (2000+1000):15 = 500 – 3000:15 = 500 – 200 = 300
Ta có: 300 = 2 2 . 3 . 5 2
h, 967 – [8 + 2 . 3 2 – 24:6 + 9 - 7 3 ].5 = 967 – [8+2.9 – 4+8].5 = 967 – 30.5 = 967 – 150 = 817
Ta có: 817 = 19.43
a) 17. 85 + 15 . 17 = 300
= 17. 9 85 = 15) + 300
= 2000
b) 72. 121 + 27 .121 = 121
= 121 . ( 72 + 27 = 1)
= 12100
c) 32. 39 + 52 . 21 - 12 . 39 + 21 . 48
= ( 32 - 12).39 + 21. ( 52 + 48)
= 2880
d) 47 - ( 45.24 - 52.12) : 14
= 47 - ( 45 . 16 - 25.12) : 14
= 17
e) 102 - 60 : ( 54 : 52 - 3. 5)
= 100 - 60 : ( 25 - 15)
= 100 - 6
= 94
47 – [(45.24 – 52.12):14]
= 47 -[45.16 - 25.12):14]
= 47 - [720 - 300):14]
= 47 - [420:14]
= 47 - 30
= 17
Bài 2. Tính nhanh
a) 27 + (-2019) + (-27)
= 27 -2019 -27
=(27 - 27) -2019
=0-2019
= -2019
d) (-102) – (345 – 102)
= -102 - 345 +102
= (102 - 102) -345
= 0-345
= -345
b) (-10) + 23 + (-20) + 30
= -10 +23-20+30
= -(10+20) +23 +30
= -30 +23 +30
= (30-30) +23
= 0 +23
= 23
e) (12 + 34 – 56) – (12 – 56)
= 12 +34 -56 -12 +56
= (12-12) + (56-56) +34
= 0+0 +34
= 34
c) (-2).125.(-5).(-8).(+17)
=[(-2) . (-5)] . [ 125.(-8)] . (+17)
= 10 . (-1000).(+17)
= - 10000 . 17
= - 170000
f) 37.(-345) – 345.(-47)
= -345 . (37-47)
= -345.(-10)
=3450
47-[(45.24-52.12)]:14
= 47 - [(45.16-25.12)]:14
= 47 - (720-300) : 14
= 47 - 420 : 14
= 47 - 30
= 17
S1 = 1 + 2 + 3 + ... + 999 (999 số hạng)
= (1 + 999).999/2 = 499500
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