Write an algebraic expression to represent the total number of silver dollars that could be in a 24-gallon tank. Let d = number of silver dollars.
Data: Silver dollar (a type of fish) is 8" in length.
This is my 10 year old daughter's math homework. Can you make any sense of it? We can't. A prize if you can get any kind of answer at all.The Man is kinda down about it. That and missing out on the Nobel prize for Physics yet again.
What we need is a Maths Expert. Preferably one with fish-keeping experience.
Too early in the morning for maths homework, but apple flapjack is easy - just grate an apple into the mixture (we always add loads more oats that it says) and it makes a really lovely moist flapjack.
ReplyDeleted=24/a where a is the amount of water in gallons required to support one silver dollar at ambient temperature
ReplyDeleteCan't argue about that, old dog, except that the question says "use the [data in] the table", i.e. your expression needs to contain the length of the fish!
ReplyDeleteGood point about the chicken stock yesterday, Man - I always have been rather haphazard at following recipes. Substitute veg stock if you're a purist. Also, the missing ingredient was broken cashew nuts.
ReplyDeleteWe also received the suggestion d=24/v, where v is the volume of each fish. Apart from the fact that this expression does not include the length of the fish (as required) this leaves no room in the aquarium for any water.
ReplyDeleteWe think as this is a children's math question, the fish are meant to be alive and well.
Inches and gallons? Oh my. Takes me back to 1977. d/24v
ReplyDeleteIt was great to meet you at the market. Thought I could help out here. Although, admittedly I cheated.
ReplyDeleteHere's the answer:
you could use a variable to describe the relationship between inches of fish and required water size.
so x = gallons per inch. then
d=24/(8*x)
so if there is one gallon per inch requirement, then you could fit 3 fishes in there, if you need 3 gallons per inch, then only one can fit in there.
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I got it from here:
http://www.thecashreport.com/graded-silver-dollar/
Nice to meet you, too, Profussor. Thank you for your well-researched math-problem-solving. More on that anon - look out for Mad Math II, coming soon...
ReplyDeleteWe found the problem in a Math book, where it included the critical additional line "Assume you need 1 gallon of water for every inch of length of the fish", i.e. assume x=1 (in Daniel B's notation).
ReplyDeleteWhich is fine, except there is no reason as far as I know to assume a priori that the volume of water a fish needs is directly proportional to its length, so a more general expression is:
d = 24/f(l)
where f(l) is some (unknown) function of the fish's length "l" and l=8. However, I worried that if my daughter wrote this her teacher might suspect she was getting help.
In fact her teacher tacitly acknowledged this was a missprint by airily saying something along the lines of: "I just wanted to see what you made of it".
If this was a "proper" physics question, the last line would say something like "assume a spherical fish"
ReplyDeleteDo you call it physics, or physic in the US ;-) ?