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Tính nhanh:
1+2+3+4+5+6+7+8+9+10
=(1+9)+(2+8)+(3+7)+(4+6)+10+5
= 10 + 10 + 10 + 10 + 10+5
= 50 + 5
= 55
123*45+123*50+123*5
= 123*(45+50+5)
= 123 * 100
= 12300
K mk nha bn
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[1 x 2 x 3 x 4 x........................x100] x [679+679 x 123-679 x124]
= A x [679 x 124-679 x 124]
= A x 0
=0
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123*154-24*123-123*30.
=123.(154-24-30)
=123.100=12300
k mk nhé ,thank you nhìu
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1. 1996 ++ 3012 + 5988 + 7004
= ( 1996 + 7004 ) + ( 3012 + 5988)
= 9000 + 9000
= 18000
2.1253 + 254 + 2345 - 253 - 154
= ( 1253 - 253 ) + ( 254 - 154 )
= 1000 + 100
= 1100
3. 123 + 456 + 77 + 546
= ( 123 + 77 ) + ( 456 + 546)
= 200 + 1002
= 1202
4.50 - 5 - 5 - 5 - 5 - 5 - 5 - 5 - 5 - 5 - 5 - 5
= 50 - ( 5 x 11 )
= 50 - 55
= -5
5.143 - ( 80 + 43 )
= 143 - 123
= 20
Chúc bạn học tốt!
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( 36 + 54 ) x 7 + 7 x 9 + 7 = 90 x 7 + 7 x 9 + 7 x 1
= ( 90 + 9 + 1 ) x 7
= 100 x 7
= 700
( 36 + 54 ) x 7 + 7 x 9 + 7
= 90 x 7 + 7 x 9 + 7
= 7 x ( 90 + 9 +1 )
= 7x 100
= 700
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123x17-123-7=1961 nha