用简便方法计算1/27+2/27+3/27+.+26/27=?
问题描述:
用简便方法计算1/27+2/27+3/27+.+26/27=?
答
1/27+2/27+3/27+.+26/27=?
=1/27(1+2+3+...+26)
=1/27[(1+26)*26/2]
=1/27*(27*13)
=13