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Given: A certain Formula 1 car fuel consumption is 2.5 liters per kilometer, and the supply pump injects 11 liters of fuel per second. Every time a pit stop for refueling is needed (i.e., the fuel tank is almost empty), fuel is injected during 6.5 seconds.
Asked: In a 3.5-kilometer per lap race circuit, what is the maximum possible number of laps this car can run before it needs a new pit stop for refueling?

Fuel consumption in 3.5 km = 3.5 * 2.5 = 8.25 liters
Supply pump injects = 11 * 6.5 = 71.5 liters

Number of laps this car can run before it needs a new pit stop for refueling = 71.5/8.25 = 8.67 laps

IMO B
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Lets keep it simple:
Total capacity: 13/2*11=133/2L
Km per liter: 2.5km
Total # km= (133/2)/(5/2)=133/5km

Number of laps: Total KM with full tank / lap size
(133/5)/(7/2)=266/35= approx 8
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3.5*2.5 would be 8.75 kindly check it out!
Kinshook
Given: A certain Formula 1 car fuel consumption is 2.5 liters per kilometer, and the supply pump injects 11 liters of fuel per second. Every time a pit stop for refueling is needed (i.e., the fuel tank is almost empty), fuel is injected during 6.5 seconds.
Asked: In a 3.5-kilometer per lap race circuit, what is the maximum possible number of laps this car can run before it needs a new pit stop for refueling?

Fuel consumption in 3.5 km = 3.5 * 2.5 = 8.25 liters
Supply pump injects = 11 * 6.5 = 71.5 liters

Number of laps this car can run before it needs a new pit stop for refueling = 71.5/8.25 = 8.67 laps

IMO B
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Wouldn't 8.67 normally be rounded off to 9? Since its one of the options, how do you safely determine between the two?
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Given: A certain Formula 1 car fuel consumption is 2.5 liters per kilometer, and the supply pump injects 11 liters of fuel per second. Every time a pit stop for refueling is needed (i.e., the fuel tank is almost empty), fuel is injected during 6.5 seconds.
Asked: In a 3.5-kilometer per lap race circuit, what is the maximum possible number of laps this car can run before it needs a new pit stop for refueling?

Fuel consumption in 3.5 km = 3.5 * 2.5 = 8.25 liters
Supply pump injects = 11 * 6.5 = 71.5 liters

Number of laps this car can run before it needs a new pit stop for refueling = 71.5/8.25 = 8.67 laps

IMO B
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In this case you have to round down because they ask for the maximum number of rounds. Cant't drive half a lap.

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Wouldn't 8.67 normally be rounded off to 9? Since its one of the options, how do you safely determine between the two?

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but the stem doesn't state how full the tank is in the beginning?
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Hi gotkimherela,

This is a great question to ask, because the answer is hiding in one phrase you may have read past.

Look at what a pit stop actually does: fuel is injected for 6.5 seconds at 11 liters/second, so every refuel puts in exactly:

- 11 × 6.5 = 71.5 liters

That's the key. The question isn't asking how far the car goes from some unknown starting level - it asks for the maximum laps before it needs a new pit stop. In other words, you start right after a refuel, with a fresh 71.5 liters, and run until the tank is almost empty again (which is when the next pit stop is triggered).

So the starting level is fixed by the problem itself: a pit stop happens "when the tank is almost empty," and each pit stop adds 71.5 liters. You never need to know a separate initial amount - the refuel is the amount you work with.

From there the posted solutions line up:

- Fuel per refuel: 71.5 liters
- Distance: 71.5 ÷ 2.5 = 28.6 km
- Laps: 28.6 ÷ 3.58.17

Since you can only count laps you actually complete before the next stop, you round down to 8 - answer (B).

So the takeaway: the phrase "before it needs a new pit stop" is what pins down the starting fuel. The problem gives you the tank contents indirectly, through the refuel, rather than stating a number outright.

Answer: B
gotkimherela
but the stem doesn't state how full the tank is in the beginning?
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