Bài 2 tính bằng cách thuận tiện a 1397 + 642 - 397 + 400 - 42
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642 - 29 + 329 - 42 + 100
= ( 642 - 42 ) + ( 329 - 29 ) + 100
= 600 + 300 + 100
= 1000
Nhớ tk mình nha!
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(3214 x 42 - 27 x 3214 - 642 : 3 x15) :300
=(3214 x (42 - 27) - 642 : 3 x 15) : 300
=(3214 x 15 - 214 x 15) : 300
=(3214 - 214) x 15 : 300
=3000 x 15 :300
= 45000: 300=150
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1210 + 397 + 2790 + 503
= (1210 + 2790) + (397 + 503)
= 4000 + 900
= 4900
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2+6+8+10+14+18+....+30+34+38+42+46
=(2+46)+(6+42)+(10+38)+....+(22+26)
=48x6
=288
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\(a,2\times134\times50\)
\(=\left(2\times50\right)\times134\)
\(=100\times134\)
\(=13400\)
\(b,397\times20+397\times82-397\times2\)
\(=397\times\left(20+82-2\right)\)
\(=397\times100\)
\(=39700\)
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khoảng cách giữa 2 số là: 6-2=4
có số số hạng là: (46-2):4+1=12 (số)
tổng là: (46+2)x12:2=288
k nha
a,1397+642-397+400-42
=1397-397+642-42+400
=(1397-397)+(642-42)+400
=1000+600+400
=1000+(600+400)
=1000+1000
=2000
a,1397+642-397+400-42
=1397-397+642-42+400
=(1397-397)+(642-42)+400
=1000+600+400
Thêm (nếu cần)
"=1000+(600+400)
=1000+1000"
=2000