Question

4/6+4/6×11+4/11×16+4/16×21等于多少

Answer 1

4/6+4/6×11+4/11×16+4/16×21

=4×(1/1×6+1/6×11+1/11×16+1/16×21)

=4×[(1-1/6)/5+(1/6-1/11)/5+(1/11-1/16)/5+(1/16-1/21)/5]

=4/5×(1-1/6+1/6-1/11+1/11-1/16+1/16-1/21)

=4/5×(1-1/21)

=4/5×20/21

=16/21