lala5646
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#1
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#1
an oil tank loses 32% of its contents every hour. Peter says the tank will have lost 95% of its original contents by the end of the sixth hour. Is peter correct

how?
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mqb2766
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#2
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#2
(Original post by lala5646)
an oil tank loses 32% of its contents every hour. Peter says the tank will have lost 95% of its original contents by the end of the sixth hour. Is peter correct

how?
What percentage is left after one hour, then two hours, then ...
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mqb2766
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#3
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(Original post by Dylan8421)
Hav...
Can you delete pls and read the sticky at the top of the forum about not posting solutions if the OP has not posted any form of attempt. Thanks.
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Dylan8421
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#4
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#4
(Original post by mqb2766)
Can you delete pls and read the sticky at the top of the forum about not posting solutions if the OP has not posted any form of attempt. Thanks.
only trying to help!
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OJlongley
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#5
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#5
(Original post by lala5646)
an oil tank loses 32% of its contents every hour. Peter says the tank will have lost 95% of its original contents by the end of the sixth hour. Is peter correct

how?
Each hour that goes past, the contents of the tank drops by 32%. This is equivalent to multiplying the contents by 0.68.
The first hour starts at 100% capacity, this is then multiplied by 0.68 to get 68% total
Hour two starts at 68%, this is then multiplied by 0.68 to get 46% total.
Then do this 6 times and you'll get the answer.

The faster way to do this is to multiply 100*0.68^6
This is because you multiply it by 0.68 six times, therefore 100*0.68*0.68*0.68*0.68*0.68*0.68 = 100*(0.68)^6
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mqb2766
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#6
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#6
(Original post by Dylan8421)
only trying to help!
If you've read the forum guidelines you should realize that posting full solutions isn't generally the best way to help.
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Dylan8421
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#7
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#7
(Original post by mqb2766)
If you've read the forum guidelines you should realize that posting full solutions isn't generally the best way to help.
depends who it is.
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mqb2766
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#8
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#8
(Original post by Dylan8421)
depends who it is.
Not really.
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lala5646
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#9
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#9
wait so is he right?

(Original post by OJlongley)
Each hour that goes past, the contents of the tank drops by 32%. This is equivalent to multiplying the contents by 0.68.
The first hour starts at 100% capacity, this is then multiplied by 0.68 to get 68% total
Hour two starts at 68%, this is then multiplied by 0.68 to get 46% total.
Then do this 6 times and you'll get the answer.

The faster way to do this is to multiply 100*0.68^6
This is because you multiply it by 0.68 six times, therefore 100*0.68*0.68*0.68*0.68*0.68*0.68 = 100*(0.68)^6
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lala5646
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#10
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#10
(Original post by Dylan8421)
depends who it is.
how did u do it
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Dylan8421
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#11
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#11
(Original post by lala5646)
how did u do it
Have a look at the compound intrest section in the revision guide, its basically the same thing but getting smaller.
Last edited by Dylan8421; 1 month ago
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Catherine1973
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#12
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#12
It’s a badly worded question in that in real life it would probably lose 32% of the initial contents every hour.

With the way it’s worded it would never be empty but of course in real life it would be after 3-4 hours.
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srijan_p
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#13
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#13
This is simply exponential decay.
Assume the oil tank has 100l of fuel, and then because it's decay you should go with (1-amount being lost every period) to find the proportion of decay. Then just raise it to the power of the no. of periods you measure it across. If the answer is lower than 5l of fuel being left, the student would be correct.
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