Q&A - P4 Math

[BigDevil]

smartmummy:

Pls help! tomorrow maths exam...

2 files and 3 pens cost $12.50.A pen cost 75cents less than a file.How much does a pen cost?
Thank you in advance.
I did as follows
cost of pen []
cost of file []+75cents
5u+$1.5=$12.50
5u=$11.50
u=$2.30
A pen costs $2.30.

Is it correct?
How to do by substitute method? My son told a method (his own invention),I can't agree with him.

5u + $1.50 = $12.50
5u = $12.50 - $1.50 = $11

u = $2.20

[verykiasumummy]

smartmummy:

Pls help! tomorrow maths exam...

2 files and 3 pens cost $12.50.A pen cost 75cents less than a file.How much does a pen cost?
Thank you in advance.
I did as follows
cost of pen []
cost of file []+75cents
5u+$1.5=$12.50
5u=$11.50
u=$2.30
A pen costs $2.30.

Is it correct?
How to do by substitute method? My son told a method (his own invention),I can't agree with him.

hi smartmummy,
5u should be $11
1u --> $2.20
a pen costs $2.20.

[sleepyqueen]

smartmummy:

Pls help! tomorrow maths exam...

2 files and 3 pens cost $12.50.A pen cost 75cents less than a file.How much does a pen cost?
Thank you in advance.
I did as follows
cost of pen []
cost of file []+75cents
5u+$1.5=$12.50 if U is to represent a pen then the 5U = $12.50+$1.5 = $14, then 1U = $2.80
5u=$11.50
u=$2.30
A pen costs $2.30.

Is it correct?
How to do by substitute method? My son told a method (his own invention),I can't agree with him.

3 pen cost $0.75 x 3 = $2.25 more than a file.
therefore 5U of files = $12.50 - $2.25 = $10.25
1U = $2.05
A file cost $2.05
And hence a pen cost $2.05 + $0.75 = 2.80

Check : total cost of 3 pens: 3 x $2.80 = $8.40
total cost of 2 files : 2 x $2.05 = $4.10
total cost of 2 files and 3 pens = $12.50 #

[smartmummy]

Ooops… Thanks BigDevil and verykiasumummy!

[smartmummy]

sleepyqueen:

smartmummy:

Pls help! tomorrow maths exam...

2 files and 3 pens cost $12.50.A pen cost 75cents less than a file.How much does a pen cost?
Thank you in advance.
I did as follows
cost of pen []
cost of file []+75cents
5u+$1.5=$12.50 if U is to represent a pen then the 5U = $12.50+$1.5 = $14, then 1U = $2.80 Why we need to add $1.5?,sorry can't get it.My son also said something like this.
5u=$11.50
u=$2.30
A pen costs $2.30.

Is it correct?
How to do by substitute method? My son told a method (his own invention),I can't agree with him.

3 pen cost $0.75 x 3 = $2.25 more than a file.
therefore 5U of files = $12.50 - $2.25 = $10.25
1U = $2.05
A file cost $2.05
And hence a pen cost $2.05 + $0.75 = 2.80

Check : total cost of 3 pens: 3 x $2.80 = $8.40
total cost of 2 files : 2 x $2.05 = $4.10
total cost of 2 files and 3 pens = $12.50 #

Thank you for the answer.

[verykiasumummy]

sleepyqueen:

smartmummy:

Pls help! tomorrow maths exam...

2 files and 3 pens cost $12.50.A pen cost 75cents less than a file.How much does a pen cost?
Thank you in advance.
I did as follows
cost of pen []
cost of file []+75cents
5u+$1.5=$12.50 if U is to represent a pen then the 5U = $12.50+$1.5 = $14, then 1U = $2.80
5u=$11.50
u=$2.30
A pen costs $2.30.

Is it correct?
How to do by substitute method? My son told a method (his own invention),I can't agree with him.

3 pen cost $0.75 x 3 = $2.25 more than a file.
therefore 5U of files = $12.50 - $2.25 = $10.25
1U = $2.05
A file cost $2.05
And hence a pen cost $2.05 + $0.75 = 2.80

Check : total cost of 3 pens: 3 x $2.80 = $8.40
total cost of 2 files : 2 x $2.05 = $4.10
total cost of 2 files and 3 pens = $12.50 #

hi hi, sorry u may have read wrongly, the pen costs 75c less than the file..

[verykiasumummy]

optimistforum:

Thank you ruohoo97


On a different note - to all posters.

My P4 DS (just started P4 here in the UK) is struggling on the P3 Challenging Maths (Sabdya Sundar EPH). Is this normal, I know it is a hard book, but should he not be on to the P4 book by now. Any advice appreciated.

Thanks

i hv the same p3 challenging maths that u r talking about, and i do agree it is a little harsh on the p3 to do that book... my advice is to let them do those that they know and not force them on the hard ones in the start... by the time just before sa2, they should be in better form to ans those challenging questions..

from p2 to p3, there is not big jump in standard, a smaller jump when u compare with from p4 to p5.. so if they were given the challenging questions at the start of p3, u may kill their interest for math...

[verykiasumummy]

just888 and sleepyqueen is the same person??? :? :?

[sleepyqueen]

smartmummy:

sleepyqueen:

[quote=\"smartmummy\"]Pls help! tomorrow maths exam...

2 files and 3 pens cost $12.50.A pen cost 75cents less than a file.How much does a pen cost?
Thank you in advance.
I did as follows
cost of pen []
cost of file []+75cents
5u+$1.5=$12.50 if U is to represent a pen then the 5U = $12.50 -$1.5 = $11, then 1U = $2.20 Why we need to add $1.5?,sorry can't get it.My son also said something like this. Should be subtract $1.50
You see
2 files = 2 pens + 1.50 ;
therefore 2 files + 3 pens = (2 files + 1.50) +3 pens = $12.50

5u=$11.50
u=$2.30
A pen costs $2.30.

Is it correct?
How to do by substitute method? My son told a method (his own invention),I can't agree with him.

3 pen cost $0.75 x 3 = $2.25 more than a file.
therefore 5U of files = $12.50 - $2.25 = $10.25
1U = $2.05
A file cost $2.05
And hence a pen cost $2.05 + $0.75 = 2.80

Check : total cost of 3 pens: 3 x $2.80 = $8.40
total cost of 2 files : 2 x $2.05 = $4.10
total cost of 2 files and 3 pens = $12.50 #

Thank you for the answer.[/quote]Alert smartmummy!!! I made a mistake in the question, the cost of the pen is supposed to be less than the file. Here is the corrected answer:

3 pen cost $0.75 x 3 = $2.25 less than a file.
therefore 5U of files = $12.50 + $2.25 = $14.75
1U = $2.95
A file cost $2.95
And hence a pen cost $2.95 - $0.75 = $2.20

Check : total cost of 3 pens: 3 x $2.20 = $6.60
total cost of 2 files : 2 x $2.95 = $5.90
total cost of 2 files and 3 pens = $12.50 #


Thanks verykiasumummy for pointing out. :salute:

[smartmummy]

ok sleepyqueen, got it.Thanks verykiasumummy!