(1+3+5+7+……+39+41)/(2+4+6+8+……+40+42)

问题描述:

(1+3+5+7+……+39+41)/(2+4+6+8+……+40+42)

(1+3+5+7+……+39+41)/(2+4+6+8+……+40+42)
=[20(1+41)+21]/[20(2+42)+22]
=[20*42+21]/[20*44+22]
=861/902