SOLUTION: 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?

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
---------------------------------
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
--------------------------------
I can check this by converting to decimals:

Close enough
RELATED QUESTIONS
One invention saves 30 % on fuel; a second saves 45 percent; a third saves 25%. If you... (answered by lauramg012)

Each of two inventions saves 40% on fuel. If you use both inventions, what percent of... (answered by Alan3354)

Each of two inventions saves 40% on fuel. If you use both inventions, what percent of... (answered by robertb)

Heather is collecting dimes she saves one dime on the first day two dimes on the second... (answered by jim_thompson5910)

Heather is collecting dimes. She saves one dime on the first day, two dimes on the second (answered by jsmallt9)

if a discount of 25% off the retail price of a desk saves mark $45, how much did he pay... (answered by Rcmathtutor)

Dave and bill each start saving today. Dave saves 30 cents per day. Bill saves 1 cent on... (answered by mananth)

A student decides to follow a simple scheme to save money. She puts aside 5 peso the... (answered by ikleyn)

Heather is collecting dimes. She saves 1 dime on the 1st day, 2 dimes on the 2nd day & 3... (answered by josmiceli)