we know that Bob can do the whole job in 14 hours, how much of the work has he done in 1 hour only? well since he can do the whole lot in 14 hours in 1 hour he has only done 1/14 th of the job.
we know that James can do it in 18 hours, a bit slower, so in 1 hour he has done only 1/18 th of the job.
let's say it takes both of them working together say "t" hours, so in 1 hour Bob has done (1/14) of the work whilst James has done (1/18) of the work, the whole work being t/t or 1 whole, so for just one hour that'd 1/t done by both Bob and James.
70% equals to 70/100 in fraction form.
But, you need to write it in simplest form. so, divide both of them from 10 'cause they both can divide completely by it.
70/100 = 7/10
so, your answer is 7/10
Answer with explanation:
Presume that, initial water level to be, 0 mm, at a time t=0.
And water level is rising at the rate of 
.
After 6.2 years level of water will be =1.8 × 6.2
=11.16 mm
→Averge, that is increase in water level after 6.2 years is given by
→→Rate of Depreciating of water level is given by = Negative of Increase of water level=
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