Question

小学简便计算题10×11分之一加11×12分之一加12×13分之一加13×14分之一加14×15分之一,（要简便、）

Answer 1

1/(10×11)+1/(11×12)+1/(12×13)+1/(13×14)+1/(14×15)

=1/10-1/11+1/11-1/12+1/12-1/13+1/13-1/14+1/14-1/15

=1/10-1/15

=3/30-2/30

=1/30