Question 193489: one invention saves 30% on fuel; a second saves 45%;a third, 25%. if you use all three inventions at once how much can you save? Answer by josmiceli(19441) (Show Source):
You can put this solution on YOUR website! Say you used the inventions on a tank that holds gallons of fuel. With the 1st invention,
you'd only use 70 gallons to go a far as you went
on a tankful before. Call that distance mi
With the 2nd invention, you'd use 55 gallons
With the 3rd invention, you'd use 75 gallons
The fuel efficiencies are:
No inventions: mi/gal
1st invention: mi/gal
2nd invention: mi/gal
3rd invention: mi/gal
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These are RATES of fuel usage. I can add
the rates to get a combined rate mi/gal
That's how much of the 100 gallon tank
you'd use to go mi so you would
save gallons = 78.166% saved
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I can check this by converting to decimals:
Close enough
