1⼀11+1⼀12+1⼀13+1⼀14+1⼀15+1⼀16+1⼀17+1⼀18+1⼀19+1⼀20

2024-12-23 05:13:30
推荐回答(1个)
回答1:

原式=1X10/(11+12+13+14+15+16+17+18+19+20)/2=10/15.5=20/31