TÍNH NHANH
a, 35.34+35.86+65.75+65.45
b, 21.72-11.72+90.72+49.125.16
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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
a) 35.34 + 35.86 + 65.75 + 65.45
= 35. ( 34 + 86 ) + 65 . ( 75 + 25 )
= 35 . 120 + 65 . 100
= 4200 + 6500
= 10700
b) 21.49 - 11.49 + 90.49 + 49.125.16
= 49 . ( 21-11+90) +49 .125.8.2
= 49 .100 + 49 .1000 .2
= 4900 + 49000 .2
= 4900 + 98000
= 102900
Hên xui nhé !!!
a)
\(\Rightarrow35.\left(34+86\right)+65.\left(75+45\right)\)
\(\Rightarrow35.120+65.120\)
\(\Rightarrow120.\left(35+65\right)=120.100=12000\)
b)
\(\Leftrightarrow21.49-11.49+90.49+49.125.16\)
\(\Rightarrow49.\left(21-11+90+2000\right)\)
\(\Rightarrow49.2100=102900\)
a) 35 . 34 + 35 . 86 + 65 . 75 + 65 . 45
= 35 . ( 34 + 86 ) + 65 . ( 75 + 45 )
= 35 . 120 + 65 . 120
= ( 35 + 65 ) . 120
= 100 . 120
= 12000
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 = \(\frac{99\cdot100\cdot101}{3}=333300\)
A,35*34+35*86+65*75+65*45
=35*[34+86]+65*[75+45]
=35*100+65*120
=35*100+65*100+65*20
=[35+65]*100+65*20
=10000+1300=11300