1.tính nhanh
a)(56* 2,7+56*3,5)/0,62
b)371*65+371*14+629*79
c)0,48*700-2,4**45*2
d)13,5*5,1+4.,5*1+4,5*7,8*3+12,9*6,5
e)3,2*950+8*175*4+320*73
1.tính nhanh
a)(56* 2,7+56*3,5)/0,62
b)371*65+371*14+629*79
c)0,48*700-2,4**45*2
d)13,5*5,1+4.,5*1+4,5*7,8*3+12,9*6,5
e)3,2*950+8*175*4+320*73
Giải:
a) \(\dfrac{56.2,7+56.3,5}{0,62}\)
\(=\dfrac{56.6,2}{0,62}\)
\(=56.10=560\)
b) \(371.65+371.14+629.79\)
\(=371\left(65+14\right)+629.79\)
\(=371.79+629.79\)
\(=79\left(371+629\right)\)
\(=79.1000=79000\)
c) \(0,48.700-2,4.45.2\)
\(=4,8.70-4,8.45\)
\(=4,8\left(70-45\right)\)
\(=4,8.25=120\)
e) \(3,2.950+8.175.4+320.73\)
\(=32.95+32.175+32.730\)
\(=32\left(95+175+730\right)\)
\(=32.1000=32000\)
Vậy ...
Giải:
a) 56.2,7+56.3,50,6256.2,7+56.3,50,62
=56.6,20,62=56.6,20,62
=56.10=560=56.10=560
b) 371.65+371.14+629.79371.65+371.14+629.79
=371(65+14)+629.79=371(65+14)+629.79
=371.79+629.79=371.79+629.79
=79(371+629)=79(371+629)
=79.1000=79000=79.1000=79000
c) 0,48.700−2,4.45.20,48.700−2,4.45.2
=4,8.70−4,8.45=4,8.70−4,8.45
=4,8(70−45)=4,8(70−45)
=4,8.25=120=4,8.25=120
e) 3,2.950+8.175.4+320.733,2.950+8.175.4+320.73
=32.95+32.175+32.730=32.95+32.175+32.730
=32(95+175+730)=32(95+175+730)
=32.1000=32000=32.1000
__________
A=0,48 x 700 - 2,4 x 45 x 2
4,5 +3,5+2,5+1,5+0,5-4-3-2-1
A=0,48 x 700 - 2,4 x 45 x 2
4,5 +3,5+2,5+1,5+0,5-4-3-2-1
tìm tính hợp lý của biểu thức sau:
371*65+371*14+629*79
Tính (-48)+127+(-52)+73 (-38)x45+(-38)x55 (-125)+371+(-875)+629+150 271+(-392)+729+(-608+(-123) (-48)x25+25x(-52) 47x(-11)+47 56-7x8+11 -42+51+2+(-11)+40
a) \(\left(-48\right)+127+\left(-52\right)+73\)
\(=\left(-48-52\right)+\left(127+73\right)\)
\(=-100+200\)
\(=100\)
b) \(\left(-38\right)\cdot45+\left(-38\right)\cdot55\)
\(=\left(-38\right)\cdot\left(45+55\right)\)
\(=\left(-38\right)\cdot100\)
\(=-3800\)
c) \(\left(-125\right)+371+\left(-875\right)+629+150\)
\(=\left(-125-875\right)+\left(371+629\right)+150\)
\(=-1000+1000+150\)
\(=150\)
d) \(271+\left(-392\right)+729+\left(-608\right)+\left(-123\right)\)
\(=\left(271+729\right)+\left(-392-608\right)-123\)
\(=1000-1000-123\)
\(=-123\)
e) \(\left(-48\right)\cdot25+25\cdot\left(-52\right)\)
\(=25\cdot\left(-48-52\right)\)
\(=25\cdot-100\)
\(=-2500\)
f) \(47\cdot\left(-11\right)+47\)
\(=47\cdot\left(-11+1\right)\)
\(=47\cdot-10\)
\(=-470\)
g) \(56-7\cdot8+11\)
\(=56-56+11\)
\(=0+11\)
\(=11\)
h) \(-42+51+2+\left(-11\right)+40\)
\(=\left(-42+2\right)+\left(51-11\right)+40\)
\(=-40+40+40\)
\(=0+40\)
\(=40\)
a: =-48-52+127+73
=200-100
=100
b; \(=-38\left(45+55\right)=-38\cdot100=-3800\)
c: \(=-125-875+371+629+150\)
=-1000+1000+150
=150
d: =271+729-392-608-123
=1000-1000-123
=-123
e: =25(-48-52)
=25*(-100)
=-2500
f: =47(-11+1)
=47(-10)
=-470
g: =56-56+11
=11
h: =-42+2+51-11+40
=-40+40+40
=40
1, tính thuận tiện :
0,48 x 700 + 2,4 x 45 x2
13,5 x1420 + 4,5 x780 x3
0,27 x4500+ 1,35 x 550 x 2
0,18 x1230 + 0,9 x 45670 x2 + 3 x 5310 x6
1, tính thuận tiện :
0,48 x 700 + 2,4 x 45 x2
13,5 x1420 + 4,5 x780 x3
0,27 x4500+ 1,35 x 550 x 2
0,18 x1230 + 0,9 x 45670 x2 + 3 x 5310 x6
1, tính thuận tiện
0,48 x 700 + 2,4 x 45 x2
13,5 x1420 + 4,5 x780 x3
0,27 x4500+ 1,35 x 550 x 2
0,18 x1230 + 0,9 x 45670 x2 + 3 x 5310 x6
tính nhanh: 371.65+371.14+629.79
= 371 . ( 65 + 14 ) + 629 . 79
= 371 . 79 + 629 . 79
= 79 . ( 371 + 629 )
= 79 . 1000
= 79000
Bài 1 : Tính nhanh
a) 212 + 109 + 188 b) 305 + 295 + 140 c) 9 . 4 . 25 . 8 . 125
d) 35 + 56 + 65 + 44 e)277 + 194 + 206 + 123 g) 8 . 25 . 2 . 4 . 5 . 125
h) 29 . 25 + 29 . 45 + 29 . 30 i) 36 . ( 143 + 57 ) + 64 . ( 143 + 57 )
k) 491 . ( 747 + 53 ) + 491 . ( 153 + 47)
Bài 2 :Phaỉ dùng bao nhiêu chữ số để viết các số
a) từ 1 đến 99 b) từ 100 đến 999 c) từ 1000 đến 9999
Bài 4 : Tính tổng
a) M = 1 + 2 + 3 +... + 103 b) N = 3 + 7 + 11 +...+ 99 c) C = 1+ 11 + 21 + ... + 991
a) 4895 : 5 - 2765 : 5 | b) 7236 : (3 x 4) |
c) (964 x 48) : 4 | d) (371 x 56) : 7 |
a) (4895 - 2765) : 5 = 426
b) 7236 : ( 3 x 4) = 7236 : 12 = 603
c) ( 964 x 48) : 4 = 11 568
d) (371 x 56) : 7 = 2968
a) 4895 : 5 - 2765 : 5
= 979 - 553
= 426
b) 7236 : (3 x 4)
= 7236 : 12
= 603
c) (964 x 48) : 4
= 46272 : 4
= 11568
d) (371 x 56) : 7
= 20776 : 7
= 2968