Hello eagertolearn Originally Posted by
eagertolearn A pollutant has leaked into a water tank containing 2000 gallons of water. The tank now is 3% pollutant. How much clean water should be added to the tank to decrease the concentration of the pollutant to a safe level of 0.5%?
TIA!
Can I suggest an alternative method, using ratios?
Initially, there are 2000 gallons of water in the tank, which is 97% of the total amount. The remaining 3% is pollutant. So the ratio of water to pollutant is $\displaystyle 97:3$. The amount of pollutant in the tank is therefore: $\displaystyle \frac{3}{97}\times 2000= 61.856$ gallons
After adding extra water, this has to be 0.5% of the total, the other 99.5% being water. So now the ratio of water to pollutant is $\displaystyle 99.5:0.5=199:1$. Since there are still $\displaystyle 61.856$ gallons of pollutant in the tank, the amount of water must now be:$\displaystyle 61.856\times199 = 12309$ gallons
Therefore, we must add $\displaystyle 12309 - 2000 = 10309$ gallons of water.
Grandad