Graphs..

[Lingglingg]

This is very easy and straight forward, but the answers on my textbook isn’t the same as my answers?!! For 2b and 2c, the textbook answers seem to be wrong. Have I missed anything??

What are your answers to them please?? I’m so frustrated with this textbook!!!

 

[lev888]

This is very easy and straight forward, but the answers on my textbook isn’t the same as my answers?!! For 2b and 2c, the textbook answers seem to be wrong. Have I missed anything??

What are your answers to them please?? I’m so frustrated with this textbook!!!

Please post your answers and explanation.

 

[Lingglingg]

Ok.

2b. £1x50pens+£0.90x10pens
=£59

But then, after looking at the “Hint” in the orange box, perhaps it should be £1x49pens+£0.90x11pens =£58.90

But either way, my textbook answer for this question isn’t the same as both of these.

2c. If 2b is incorrect, probably my calculations for 2c from my understanding and approach to the question also is also applied incorrectly... in the same way.

So 2c. after applying the logic of the “Hint”, for the first 49 pens, £1x49pens =£49, for the 50th to 74th pens, £0.90x25pens =£22.50. £49+£22.50=£71.50.

Budget of £75-£71.50=£3.50.
At £0.80 per pen, £3.50/£0.80 can get 4 more pens.

So 49+25+4 = 78 pens


Ok...
So after all the above effort, I now know I’m thinking about this too much.
The answer on the textbook is £54 for 2b abd 149 pens for 2c. I got it now!!! Haha

 

[Steven G]

How can we tell who is correct if you did not include the answers from you and the book? Or do you just want someone here to just give you the answer? Please read the forum guidelines which states that to receive help you must show your work so a helper can show you where you have a mistake and give some guidance. Thank you.

 

[lev888]

Ok.

2b. £1x50pens+£0.90x10pens
=£59

But then, after looking at the “Hint” in the orange box, perhaps it should be £1x49pens+£0.90x11pens =£58.90

But either way, my textbook answer for this question isn’t the same as both of these.

2c. If 2b is incorrect, probably my calculations for 2c from my understanding and approach to the question also is also applied incorrectly... in the same way.

So 2c. after applying the logic of the “Hint”, for the first 49 pens, £1x49pens =£49, for the 50th to 74th pens, £0.90x25pens =£22.50. £49+£22.50=£71.50.

Budget of £75-£71.50=£3.50.
At £0.80 per pen, £3.50/£0.80 can get 4 more pens.

So 49+25+4 = 78 pens


Ok...
So after all the above effort, I now know I’m thinking about this too much.
The answer on the textbook is £54 for 2b abd 149 pens for 2c. I got it now!!! Haha

2b. Yes, you have to take into account the open circles. £1x49pens+£0.90x11pens would be my answer.
2c. 78 looks right.
Not sure where the textbook answer come from.

 

[Steven G]

How can we tell who is correct if you did not include the answers from you and the book? Or do you just want someone here to just give you the answer? Please read the forum guidelines which states that to receive help you must show your work so a helper can show you where you have a mistake and give some guidance. Thank you.

To OP: I apology for my last post but your post with your work was not there when I made my post.

 

[Steven G]

Ok.

2b. £1x50pens+£0.90x10pens
=£59

But then, after looking at the “Hint” in the orange box, perhaps it should be £1x49pens+£0.90x11pens =£58.90

But either way, my textbook answer for this question isn’t the same as both of these.

2c. If 2b is incorrect, probably my calculations for 2c from my understanding and approach to the question also is also applied incorrectly... in the same way.

So 2c. after applying the logic of the “Hint”, for the first 49 pens, £1x49pens =£49, for the 50th to 74th pens, £0.90x25pens =£22.50. £49+£22.50=£71.50.

Budget of £75-£71.50=£3.50.
At £0.80 per pen, £3.50/£0.80 can get 4 more pens.

So 49+25+4 = 78 pens


Ok...
So after all the above effort, I now know I’m thinking about this too much.
The answer on the textbook is £54 for 2b abd 149 pens for 2c. I got it now!!! Haha

The way you are thinking about this is fine. That is the way which you are interpreting the graph is reasonable
However I am interpreting it differently. I think, for example, if you buy 50 up to and including 74 pen that you pay £0.90 for each pen.
As a result, you pay 60*£0.90 = £54 for 60 pens.

I always feel that when doing a word problem if a student thinks about it fairly but differently than the author then that is fine and the student should not worry about 'getting the problem wrong' as they did not in my opinion. Now I am not saying that the student could think of the problem any way they want. It must be reasonable!

For the record, is the author's/teacher's answer corresponding to the way I am doing this?

 

[Steven G]

Update: I reread the problem. It states that 'the graph shows the price per pen depending on how many pens are ordered'
So now I think that your interpretation is wrong.
If you purchase 60 pens then the cost per pen is £0.90 each.
part a) Then a single pen costs £1
part b) 60 pens cost 60*£0.90 = £54
Part c) If he buys 49 pens at £1 he can spend more.
If he buys 79 pens at £0.90 then this will cost £71.1 which is less than his budget.
if he buys 99 pens at £ .8 then the cost will be £79.2 which is more than his but budget. He then can buy some pens at £.8 and the question is how many. Well £75/£.8 = 93.75. So he can buy 93 pens.

 

[Steven G]

2b. Yes, you have to take into account the open circles. £1x49pens+£0.90x11pens would be my answer.
2c. 78 looks right.
Not sure where the textbook answer come from.

Please read my post #8 and comment on my method. Thanks!

 

[lev888]

Please read my post #8 and comment on my method. Thanks!

I agree. I am probably thinking about how taxes work too much

 

[Lingglingg]

Thanks, both for looking at my question, and for answering.

I don’t know if you’ve seen the very last paragraph of my post #2 about the textbook’s answer -
“Ok...
So after all the above effort, I now know I’m thinking about this too much.
The answer on the textbook is £54 for 2b abd 149 pens for 2c. I got it now!!! Haha”

So for question 2b, in reality, no one actually will buy 49 pens at £1, and the rest at £0.90 when he/she can order all the pens at £0.90. Same concept -bulk purchase at a lower price applied, giving its answer 149pens for question 2c!!! . (This is a lot more than our original answers!)