Toán Lớp 6: a, Tính S = 4 + 7 + 10 +13 + … + 2014
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Toán Lớp 6: a, Tính S = 4 + 7 + 10 +13 + … + 2014
Comments ( 2 )
(2014-4):3+1=671
S=4 + 7 + … 2011+ 2014
S=2014+2011+……..+7+4
2S=2018 +2018+…….+2018+2018
Tổng là: 2018.671:2=677 039
$\text{S = 4 + 7 + 10 … + 2014 }$
$\text{từ 7 => 2014 có số là : }$
$\text{(2014 – 7 ) : 3 + 1 = 670 ( số ) }$
$\text{có số cặp là : }$
$\text{270 : 2 = 335 ( cặp ) }$
$\text{Vậy S = 4 + ( 7 + 2014 ) $\times$ 335 }$
$\text{= 4 + 677035 = 677039}$