A swimming pool is to be drained by cleaning. If L represents the number of litres of water in the pool `t` seconds after the pool has been plugged off to drain and `L=2000(10-t)^2dot` How fast is the water ruining out at the end of 5 seconds? What is the average rate at which the water flows out during the first 5 seconds?

Explanation

Let L represents the number of litres of water in the pool t seconds after the pool has been plugged off to drain, then



`L=200(10-t)^{2}`



`therefore` Rate at which the water is running out `=-frac{d L}{d t}`



`frac{d L}{d t}=-200.2(10-t) cdot(-1) `


`=400(10-t)`


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