Number of times the car ran out of petrol. (More detail given)?
A car ride uses a mean of 7 litres of petrol with a standard deviation of 0.5 litres. Assuming that the amount of petrol used is normally distributed.
i) If the car usually has only 8 litres in its tank, how many times in next 1000 rides will the car ran out of petrol?
After calculation answer comes to 22.8 times. Now should the answer be 22 times or 23 times. My assumption is 22 times as the 23rd time due not occur.
2006-11-01 20:00:31 · 4 answers · asked by prashmanic 4 in Science & Mathematics ➔ Mathematics
round up to 23 times. it is very close and sometimes car rides can stretch.
2006-11-01 20:02:50 · answer #1 · answered by ~Amber~ 4 · 0⤊ 0⤋
Actually, your assumption, while intuitive, has a flaw.
If you consider ONLY times where you run out of gas 22 or 23 times, look to the next decimal place - 0.8.
So, 80% of the time it will be 23, and 20% (1-0.8) will be 22.
I hope this clears up your concern.
2006-11-01 20:04:38 · answer #2 · answered by topher8128 2 · 0⤊ 0⤋
Topher 8128 is closest to right, don't listen to the other people.
See, the issue is that you're working with probabilities. Over 10,000 rides, it will run out of petrol 228 times. Since you're working with probabilites and averages anyway, I'd say 22.8 is the average.
2006-11-01 20:29:57 · answer #3 · answered by tgypoi 5 · 1⤊ 0⤋
It will be 22 because the car will not be able to finish the 23rd trip and will stop short of its destination.
2006-11-01 20:07:04 · answer #4 · answered by Roger 3 · 0⤊ 0⤋