Am i missing something?

Hey everyone,
I was reading this math question in this book of mine and it just doesn't make any sense to me, tell me if the answer makes any sense to you:

"Working with an old monetary system that used Pounds, shillings, and pence and there are 20 shillings to a pound, and 12 pence to a shilling...how much would 5 pounds, 2 shillings, and 8 pence come out to in the newer system that uses only pounds and pence (where 100 pence equals a pound like the penny to the US dollar)"

The answer given in the book is 5.13 pounds in the new system, which I didnt even come close to getting...

I multuiplied 5 pounds times 20 shillings and then tacked on the extra 2 shillings and multiplied that by 12 pence to get the total amount of pence, which I divided by 100 to get pounds and pence...tell me what you guys get...

I get 5.13 (actually, 5.1333 etc).
You have 2 shillings = 2 * 1/20 of a pound
You have 8 pence = 8 * 1/12 of a shilling = 8 * (1/12) * (1/20) = 8 * 1/240 of a pound
And then, the 5 pounds
Which comes to ~5.13 pounds or 5 pounds, 13 pence

Edit: Notice that old pence and new pence are of unequal value

There are 240 (12 x 20) pence in a pound, so:

5 pounds = 5 x 240 = 1200
2 shillings = 2 x 12 = 24
8 pence = 8 x 1 = 8

Sum: 1232 pence, 12.32 pounds

I can't explain the other answers but that's what I get...

edit: I guess the discrepancy is coming from the fact that I was assuming the pence remained the same value, whereas they assumed the pound kept the same value and everything else changed in reference.

As has been shown, the answer depends on whether
1 new pound = 1 old pound or
1 new pence = 1 new pence

Both answers are correct, but I'd probably assume that the pound was unchanged, because that is the main currency. If the pound is unchanged, the answer is 5,13 just as Zach showed.

thanks a lot guys...I completely wasnt even paying attention to the fact that the value of the new pence wasnt equal to the old pence...very good eye (or mind) to catch a little deatil like that. It had come to the point where I was mad at the author and I was minutes away before emailing him and insulting his math skills...phew, thankfully I asked you guys first. haha. Thanks yet again. :D <-Chap

ok...so maybe I'm missing something still...I still can't seem to figure the problem out...no matter what I do I can't seem to come to 5.13

sorry to be a pain, but if anyone has any more assistance...it would be very appreciated

I tryed it, i understand how you get 12.32 so i was trying to figure out how you get 5.13, i got something close but not 5.13 i got 5.32, maybe its a typo or maybe im wrong, either way consider this.

1 pound = 20 shillings, but you only have 2 shillings and since 1 shilling is equal to 12 pence our 2 shillings are equal to 24 pence
you also have 8 pence, thats total of 32 pence.

100 pence = 1 pound but we only have 32pence so thats 32/100 + 5pounds = 5.32pounds.

this is why the "new math" is retarded


sorry, I just had a really really really bad high school math class....I won't get into it...but don't you guys think that question is kind of stupid? Especially because it seems that it can be solved a few different ways?

hehe...I don't think it's stupid personally...I like a challenging math problem...especially ones I have no idea how to figure out, but that's just my preference...thankfully if you think something is stupid, you have the option of looking the other way :p

Summary:

There are two methods to solve this problem, both are correct IMHO.

A) New pound = Old pound
8 pence = 8/12 Shilling = 8/12 * 1/20 Pound = 8/240 Pound
2 shillings = 2/20 Pound

Total: 5 + 8/240 + 2/20 = 5 + 2/15 (old/new) Pound ~= 5.13 Pound

B) New Pence = Old Pence
This is litte less plausible, but the question can be interpreted this way.
5 (old) Pounds = 5*8*20 pence = 1200 pence
2 Shillings = 2 * 12 pence = 24 pence
8 pence

Total: 1200 + 24 + 8 = 1232 pence = 12.32 (new) Pounds

C) A little from each
InvariantLoop used both
5 old pounds = 5 new pounds and
32 old pence = 32 old pence
That is not correct.

yeah i figured something was wrong thats why the result seemed kinda right. But i have to agree with Waldo, questions that are constructed in a way that give you 2 different answers are lacking some info.

ah ha awesome, thanks a lot Drax...and in terms of Waldo's comments...this question is very important to me and I'm really hurt that you would say something like that about the math I'm doing...:( hehe, I totally get your point and I think the question really is ridiculous...I sadly need to finish everything I start so I had to be on the side of the question momentarily, now that it's out of the way (thanks only to Drax and a few other tips), I can move on with my life and (hopefully) never have to make any ridiculous programs like this ever again...thanks again!

1/4 of a penny (1/4 d), was a Farthing, or a bird
1/2 of a penny (1/2 d), was a Ha'penny
A penny was a penny (1d).
3 x penny, (3d), was a 12 sided coins called a thre'penny bit.
6 x penny, (6d), was a sixpence, or a tanner.
12 x penny was a shilling (1/-), or a bob
2 x shillings (2/-), was a two shilling piece, 2 bob or a florin.
2 shillings and sixpence (2/6), was a half crown
5 x shillings (5/-) was a crown, although I don't remember crown coins.
10 x shillings (10/-), was ten bob, a brown note
20 x shillings (£1/-/-) was a pound a green note
21 x shillings (21/-), was a guinea
5 x pounds was a fiver and was a blue note

1 new pound = 1 old pound
1 new penny = 1/100 of a pound.