Tính hợp lí:
35.34 + 35.56 + 65.75 + 65.45
Bài 2. Tính bằng cách hợp lí nhất:
a) 38. 63 + 37. 38 b) 12.53 + 53. 172– 53. 84
c) 35.34 +35.38 + 65.75 + 65.45 d) 39.8 + 60.2 + 21.8
e) 36.28 + 36.82 + 64.69 + 64.41
a)38.63+37.38
=38.(63+37)
=38.100
=3800
a) \(=38\left(63+37\right)=38.100=3800\)
b) \(=53\left(12+172-84\right)=53.100=5300\)
c) \(=35\left(34+38\right)+65\left(75+45\right)=35.72+65.120=10422\)
d) \(=39.8+15.8+21.8=8\left(39+15+21\right)=8.75=600\)
e) \(=36\left(28+82\right)+64\left(69+41\right)=36.110+64.110=110\left(36+64\right)=110.100=11000\)
Câu 1: Thực hiện phép tính (tính hợp lí nếu có thể)
a) 35.34+35.86+65.75+65.45
b)7.5^2-32:2^3+9
a, 35.34 + 35.86 + 65.75 + 65.45
= 35.(34 + 86) + 65.(75 + 45)
= 35.120 + 65.120
= 120.(35+65)
= 120.100
= 12000
b, \(7.5^2-32:2^3+9\)
= 7.25 - 32:8 + 9
= 175 - 4 + 9
= 180
Thực hiện phép tính (Hợp lý nếu có thể) :
a) 35.34 + 35.86 + 65.75 + 65.45
a) 35.34 + 35.86 + 65.75 + 65.45 =
( 35 + 65 ) x ( 34 + 86 ) + ( 75 + 45 )
100 x 120 x 120
100 x 14400
1440000
\(35\cdot34+35\cdot86+65\cdot75+65\cdot45\\ =35\cdot\left(34+86\right)+65\cdot\left(75+45\right)\\ =35\cdot120+65\cdot120\\ =120\cdot\left(35+65\right)\\ =120\cdot100\\ =12000\)
Tính nhanh: 35.34 + 35,86 + 65.75 + 65.45.
35.34 + 35.86 + 65.75 + 65.45 = 35.(34 + 86) + 65.(75 + 45) = 120.35+120.65 -120.(35 + 65) = 12000
35.34+38.35.38+65.75+65.45
35.34+35.38+65.75+65.45
35.34+35.38+65.75+65.45
=35.(34+38)+65.(75+45)
=35.72+65.120
=2520+7800
=10320
35.34+35.38+65.75+65.45
=35(34+38)+65(75+45)
=35.72+65.120=2520+7800=10320
35.34+35.38+65.75+65.45
35 . 34 + 35 . 38 + 65 . 75 + 65 . 45
= 35 . (34 + 38) + 65 . (75 + 45)
= 35 . 72 + 65.120
= 2520 + 7800
= 10320
~Study well~
#QASJ
35.34+35.38 + 65.75 + 65.45
= 35.(34+38)+ 65 . (45 + 75)
= 2520 + 7800
= 10320.
tính A = 1.2 + 2.3 + 3.4 + ..... + 99.100
35.34 + 35.86 + 65.75 + 65.45
Xét\(3A=1\cdot2\left(3-0\right)+2\cdot3\left(4-1\right)+\cdot\cdot\cdot+99\cdot100\left(101-98\right)\)
\(3A=1\cdot2\cdot3-0\cdot1\cdot2+2\cdot3\cdot4-1\cdot2\cdot3+...+99\cdot100\cdot101-98\cdot99\cdot100\)
\(3A=99\cdot100\cdot101\)
\(\Rightarrow A=33\cdot100\cdot101=30300\)
A = 1 . 2 + 2 . 3 + 3 . 4 + ... + 99 . 100
3A = 1 . 2 . 3 + 2 . 3 . 3 + 3 . 4 . 3 + ... + 99 . 100 . 3
3A = 1 . 2 . ( 3 - 0 ) + 2 . 3 . ( 4 - 1 ) + 3 . 4 . ( 5 - 2 ) + ... + 99 . 100 . ( 101 - 98 )
3A = 1. 2 . 3 - 0 . 1 . 2 6 2 . 3 . 4 - 1 . 2 . 3 + 3 . 4 . 5 + 2 . 3 . 4 + ... + 99 . 100 . 101 - 98 . 99 . 100
3A = ( 1 . 2 . 3 - 1 . 2 . 3 ) + ( 2 . 3 . 4 - 2 . 3 . 4 ) + ... + ( 98 . 99 . 100 - 98 . 99 . 100 ) + ( 99 . 100 . 101 - 0.1 . 2 )
3A = 0 + 0 + 0 + ... + 0 + 99 . 100 . 101 - 0 . 1 . 2
3A = 99 . 100 . 101 - 0
A = \(\frac{99\cdot100\cdot101}{3}=333300\)
\(35\cdot34+35\cdot86+65\cdot75+65\cdot45=35\left(34+86\right)+65\left(75+45\right)\)
\(=35\cdot120+65\cdot120\)
\(=120\left(35+65\right)\)
\(=120\cdot100=12000\)
35.34+35.38+65.75+65.45
35.34+35.38+65.75 + 65.45= (35.34+35.38)+(65.75 + 65.45)
= 35.(34+38)+65.(75+45)
=35.72+65.120
=7.5.6.12+13.5.12.10=12.5(7.6+13.10)=60.172=10320