# Problem with percentages.

Hi,

Can any one help with this? I can see that the answer to part (a) is 1750, but I can't get part (b). Thanks in advance for any help.

Last year, a town recycled 8750 tonnes of waste, of which 20% was paper. Five years ealier, the town recycled 1130 tonnes of waste paper.

(a) Find the amount of paper that was recycled last vear, in tonnes to three significant figures.

(b) Show that the amount of paper that was recycled has risen by approximately 52% over the five year period.
Original post by Corries1
Hi,

Can any one help with this? I can see that the answer to part (a) is 1750, but I can't get part (b). Thanks in advance for any help.

Last year, a town recycled 8750 tonnes of waste, of which 20% was paper. Five years ealier, the town recycled 1130 tonnes of waste paper.

(a) Find the amount of paper that was recycled last vear, in tonnes to three significant figures.

(b) Show that the amount of paper that was recycled has risen by approximately 52% over the five year period.

What have you tried so far in part (b)?

In part (b), knowing that there has been an increase of approximately 52%, I have multiplied the 1130 by 1.52. I also used the change/original X 100 but that produces 54.86....
Original post by TypicalNerd
What have you tried so far in part (b)?
Original post by Corries1

In part (b), knowing that there has been an increase of approximately 52%, I have multiplied the 1130 by 1.52. I also used the change/original X 100 but that produces 54.86....

I think both are perfectly correct approaches.

I reckon there is a typo in the question and it should read “Show that the amount of paper that was recycled has risen by approximately 55% over the five year period.”

That, or the line “Five years ealier, the town recycled 1130 tonnes of waste paper.” should read as “Five years ealier, the town recycled 1150 tonnes of waste paper.”
(edited 11 months ago)
Hi,

Thanks again for your reply. I thought that there was a mistake in the question but was afraid that I was missing something.
Original post by Corries1
Hi,

Can any one help with this? I can see that the answer to part (a) is 1750, but I can't get part (b). Thanks in advance for any help.

Last year, a town recycled 8750 tonnes of waste, of which 20% was paper. Five years ealier, the town recycled 1130 tonnes of waste paper.

(a) Find the amount of paper that was recycled last vear, in tonnes to three significant figures.

(b) Show that the amount of paper that was recycled has risen by approximately 52% over the five year period.

Firstly, find 20% of 8750 which is 8750*0.2 = 1750.
Then In order to find the percentage increase, you use the formula, ((New-Original)/ Original))*100
((1750-1130)/1130))*100 = 54.86 which is pretty close to 52% or 55% (according to other comments
Hi,

Thanks for your reply. As per my replies above, I tried this approach and got the same answer as you, naturally. However, the information in the question stated that the increase was 'approximately' 52% which suggests that the real answer has been rounded to 52%, which in turn means that the real answer is between 51.5 but no greater than 52.2. So, anything outside of that range is wrong and means that the given information is wrong on some level.
Original post by π/2=Σk!/(2k+1)!!
Firstly, find 20% of 8750 which is 8750*0.2 = 1750.
Then In order to find the percentage increase, you use the formula, ((New-Original)/ Original))*100
((1750-1130)/1130))*100 = 54.86 which is pretty close to 52% or 55% (according to other comments
Sorry, I meant 'but less than 52.5'.
Original post by Corries1
Sorry, I meant 'but less than 52.5'.

As typicalnerd suggests, Id guess its a typo in the question and 1130 should have been 1150. It cancels down to 12/23 which is ~52%.