\(116​+31​+115​\)

\(=(611+511)+13=(116​+115​)+31​\)

\(=1111+13=1+13=33+13=43=1111​+31​=1+31​=33​+31​=34​\)

bài 2:

\(12+16+112+12021​+61​+121​+201​\)

\(=(12+120)+(16+112)=(21​+201​)+(61​+121​)\)

\(=1120+14=1120+520=1520=34=2011​+41​=2011​+205​=2015​=43​\)

bài 3: 

a) \(32⋅45⋅23=(32⋅23)⋅45=1⋅45=4523​⋅54​⋅32​=(23​⋅32​)⋅54​=1⋅54​=54​\)

b) \(67⋅53⋅76=(67⋅76)⋅53=1⋅53=5376​⋅35​⋅67​=(76​⋅67​)⋅35​=1⋅35​=35​\)

bài 4: 

a) \(25⋅14+34⋅25=25⋅(14+34)=25⋅1=2552​⋅41​+43​⋅52​=52​⋅(41​+43​)=52​⋅1=52​\)

b) \(611:23+511:23=(611+511):23=1:23=32116​:32​+115​:32​=(116​+115​):32​=1:32​=23​\)

a) \(347×245374​×254​\)

    \(=257×145=35035=10=725​×514​=35350​=10\)

b) \(45:12+17354​:21​+317​\)

   \(=85+173=58​+317​\)

    \(=10915=15109​\)

c) \(513−216531​−261​\)

  \(=163−136=316​−613​\)

  \(=326−136=196=632​−613​=619​\)

d) \(412:214421​:241​\)

  \(=92:94=4518=29​:49​=1845​\)

2,987,992

=67

con cấ rất vui vì sống dưới nước

đỏ; chậm; trắng; nhanh

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Tao lớp 4