Math Is Fun Forum

Shmeeztut

Member

Registered: 2009-04-14

Posts: 2

Percentages

Please help me with these two questions, I don't really understand what the difference is. ><

In 2004, the cost of organizing the concert was $385.

In 2005 the cost was 10% less than in 2004.

Calculate the cost in 2005.

And then the next question on the paper...

The cost of $385 in 2004 was 10% more than the cost in 2003.

Calculate the cost in 2003.

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Percentages

Hi Shmeeztut;

The cost of the concert in 2004 is 385 dollars, since the cost in 2005 is 10% less  we can say that the cost of the concert in 2005 is 90% of  $385. (Remember 100% - 10% = 90%). Now just do 385 times by .9 (90%/100% = ,9) and this equals $346.50 This is the cost of the concert in 2005. This makes sense because we knew it had to be less.

The cost in 2004 was 10% greater than in 2003 that means it was 100% + 10% more or 110% this is just 110/100 or 1.1 (this is how you convert any percent to a decimal so you can calculate with it). We now divide the $385 by 1.1 and get $35. This how much more the concert in 2004 is. Just do 385 - 35 = $350 this is what the concert in 2003 costs. This again makes sense because it had to be less.

See if this makes anything clearer for you. Work a few more problems like this one and it might become a little bit easier. Also ask the teacher to help you out a little. If none of that helps, its not the end of the world, just repost here.

bobbym

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

smiyc86

Member

Registered: 2009-03-19

Posts: 78

Re: Percentages

a shortcut :

if the cost decreases 10% i.e. 1/10

the prev it shud have been 1/(10-1) = 1/9 times more than this year

if the cost wud have increased by 1/10

the prev year it shud have been 1/(10+1) = 1/11 times less than this year

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I love Maths and Music ... dunno which more

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Percentages

Hi smiyc86;

   True, I didn't want to confuse him with any tricks, so I tried to be plain. If he comes back maybe you can explain it better than I can.

bobbym

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

suresh1969

Guest

Re: Percentages

Yes, Bobbym's answer is much simpler than any other's.

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Percentages

Hi suresh1969

   Thats because I am a simpleton. Just ask anybody for confirmation of that fact. You really find out how much you know about something when you try to explain it in simple terms. Its the hardest thing in the world to do. I remember a story about David Hilbert along those lines.

I really do think that identity's post to you
http://www.mathisfunforum.com/viewtopic.php?id=11996
is really a good example of a simple and lucid answer.

bobbym

Last edited by bobbym (2009-04-19 20:43:33)

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.