2⼀1+3⼀1+3⼀2+4⼀1+4⼀2+4⼀3+5⼀1+5⼀2+5⼀3+5⼀4...+50⼀49

2024-12-24 12:00:49
推荐回答(1个)
回答1:

2/1+3/1+3/2+4/1+4/2+4/3+5/1+5/2+5/3+5/4...+50/49
=2/1+2/2+2/3+2/4+……+2/49
=(2/1+2/49)×49÷2
=25×49÷2
=612.5