a) \(198+789+502+311\)
\(=\left(198+502\right)+\left(789+311\right)\)
\(=700+1100\)
\(=1800\)
b) \(15.6.4.125.8\)
\(=\left(15.4\right).6.\left(125.8\right)\)
\(=60.6.1000\)
\(=360000\)
c) \(367+129+133+371+17\)
\(=\left(367+133\right)+\left(129+371\right)+17\)
\(=500+500+17\)
\(=1000+17\)
\(=1017\)
d) \(37.64+37.35+37\)
\(=37.\left(64+35+1\right)\)
\(=37.100\)
\(=3700\)
e) \(3.25.8+4.37.6+2.38.12\)
\(=\left(3.8\right).25+\left(4.6\right).37+\left(2.12\right).38\)
\(=24.25+24.37+24.38\)
\(=24.\left(25+37+38\right)\)
\(=24.100\)
\(=2400\)
f) \(136.48+16.272+68.20.2\)
\(=136.48+16.2.136+68.2.20\)
\(=136.48+32.136+136.20\)
\(=136.\left(48+32+20\right)\)
\(=136.100\)
\(=13600\)
g) \(1+6+11+16+...+46+51\)
Số số hạng là :
\(\left(51-1\right):5+1=11\) ( số )
Tổng là :
\(\left(1+51\right)\times11:2=286\)
Chúc bạn học tốt
