1/9*10+1/10*11+1/11*12+1/12*13.1/100*101=

问题描述:

1/9*10+1/10*11+1/11*12+1/12*13.1/100*101=

=1/9-1/10+1/10-1/11+...+1/100-1/101=1/9-1/101=92/909