Question 901827
A large pump can fill a water tank in 6 hours, and a smaller pump can fill it in 10 hours. In order to fill an empty tank, the large pump is operated for 3 hours, and then the small pump is also turned on. In total, how many hours will be required to fill the tank in this way?
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let x=time when both pumps are working
let(3+x)=total time required to fill tank
1/6=work rate of large pump
1/10=work rate of small pump
1/6+1/10=5/3+3/30=8/30=4/15=work rate with both pumps turned on
..
{{{3/6+x/10+4x/15=1}}}
lcd=30
15+3x+8x=30
11x=15
x=15/11=1.36 hrs
3+x=4.36 hrs
how many hours will be required to fill the tank in this way? 4.36