1÷(1/5+1/6)
=1÷11/30
=30/11
答:由甲、乙合作,还需要30/11小时完成.
{1-(1/60-1/96)×[88-(1/12÷1/96)]}÷1/96
=[1-1/160×(88-8)]÷1/96
=(1-1/160×80)÷1/96
=(1-1/2)÷1/96
=1/2÷1/96
=48
答:甲共干了48分钟.
1/2÷5=1/10
1/5÷3=1/15
1/6÷2=1/12
(1/10+1/15+1/12)÷2=1/8
1/8-1/15=7/120
1÷7/120=120/7
1/8-1/12=1/24
1÷1/24=24
1/8-1/10=1/40
1÷1/40=40
答:甲单独做需120/7天,乙单独做需24天,丙单独做需40天.