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a) 98 + 3 + 97 +2
= (98 +2) + ( 97 + 3)
= 100 + 100 = 200
56 + 399 + 1 + 4
= (56 + 4) +( 399 + 1)
= 60 + 400 = 460
b) 364 + 136 + 219 + 181
= (364 + 136) + (219 + 181
= 500 + 400 = 900
178 277 + 123 + 422
= (178 + 422) + (277 + 123)
= 600 + 400 = 1000
* Bạn tham khảo nhé *
1212 ++ 1616 ++ 112112 ++ 120120 ++ 130130 ++ 142142 ++ 156156
== 11×211×2 ++ 12×312×3 ++ 13×413×4 ++ 14×514×5 ++ 15×615×6 ++ 16×716×7 ++ 17×817×8
== 1111 −− 1212 ++ 1212 −− 1313 ++ 1313 −− 1414 ++ 1414 −− 1515 ++ 1515 −− 1616 ++ 1616 −− 1717 ++ 1717 −− 1818
== 1111 −− 1818
== 8888 −− 1818
== 78
\(\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20}+\dfrac{1}{30}+\dfrac{1}{42}+\dfrac{1}{56}+\dfrac{1}{72}+\dfrac{1}{90}\)
\(=\dfrac{1}{1\cdot2}+\dfrac{1}{2\cdot3}+\dfrac{1}{3\cdot4}+\dfrac{1}{4\cdot5}+\dfrac{1}{5\cdot6}+\dfrac{1}{6\cdot7}+\dfrac{1}{7\cdot8}+\dfrac{1}{8\cdot9}+\dfrac{1}{9\cdot10}\)
\(=1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{6}+\dfrac{1}{6}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{8}+\dfrac{1}{8}-\dfrac{1}{9}+\dfrac{1}{9}-\dfrac{1}{10}\)
\(=1-\dfrac{1}{10}\)
\(=\dfrac{9}{10}\)
\(a.98+3+97+2\)
\(=\left(98+2\right)+\left(97+3\right)\)
\(=100+100\)
\(=200\)
\(56+399+1+4\)
\(=\left(56+4\right)+\left(399+1\right)\)
\(=60+400\)
\(=460\)
\(b.364+136+219+181\)
\(=\left(364+136\right)+\left(219+181\right)\)
\(=500+400\)
\(=900\)
\(178+277+123+422\)
\(=\left(178+422\right)+\left(277+123\right)\)
\(=600+400\)
\(=1000\)
\(HocTot!!!\)
\(@VR\)
56+ 39 + 1 + 4
= ( 56 + 4 ) + ( 39 + 1 )
= 60 + 40
= 100
/HT\
56 + 39 + 1 + 4
= ( 56 + 4 ) + ( 39 + 1 )
= 60 + 40
= 100
Hok tốt