Question

The summer has ended and it’s time to drain the swimming pool. 20 minutes after pulling the plug, there is still 45 000L of water in the pool. The pool is empty after 70 minutes.

Answer 1

Hi,

it'took 70 minutes to empty the pool.  

After 20 it's stay 45 000 litres.   So in 50 minutes, 45 000 litres are gone.  

So  :    45 000 / 50 =  4500/5 = 9*5 *100 /5 = 900

900 litres is off  every minute.

So the  pool contained  :  900 *70 =  63 000 litres  in the beginning.