1+4+7+10+13+16+19+22+25+28+31+34+37+40+43+46+49 用脱式计算
问题描述:
1+4+7+10+13+16+19+22+25+28+31+34+37+40+43+46+49 用脱式计算
答
1+4+7+10+13+16+19+22+25+28+31+34+37+40+43+46+49
=(1+49)+(4+46)+(7+43)+(10+40)+(13+37)+(16+34)+(19+31)+(22+28)+25
=50*8+25
=400+25
=425