Q&A - P3 Math
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tianzhu:
Hi tianzhu,
Hi MathIzzzFunMathIzzzFun:
Supposing the question is:
\"Mr Lim is distributing some sweets to his students. When he gives 4 sweets to each student, he would have 15 sweets left. When he gives 6 sweets to each student, there would be 3 sweets left. How many sweets does he have? \" What would be the answer ?
Good Morning.
Let's take a look at the original question.
Mr Lim has some sweets and packets. When he packs the 4 sweets per packet, there would be 15 sweets left. When he packs 6 sweets per packet, there would be 3 sweets left. How many sweets does he have?
Perhaps, the question should be rephrased in another way so as to have a apple to apple comparison.
Mr Lim has some sweets and students. When he gives 4 sweets per student, there would be 15 sweets left. When he gives 6 sweets per student, there would be 3 sweets left. How many sweets does he have?
Best wishes
excellent, that's a better way to rephrase the question.
Basically, the contention here is why would one conceive that number of students will be determinate in this case whereas the number of packets is not as in the original question.
cheers. -
cimman:
Hi cimman,Hi MathIzzzFun
I suppose another way to look at problems like this is to determine if there is a physical entity involved ie. packets, students, etc.. vs a virtual entity ie. groups. Most of these questions uses groups, ie. groups of 4, groups of 6, etc...
If a physical item is involved, then the implied assumption should be that all of the physical items should be used in the grouping, ie. in the case of the packets, all of the packets should be used to group 4 sweets or 6 sweets. In this case, then it will constrain the solution to use the same multiple for both groupings.
In the case of students in a class, it is much clearer why the implied assumption holds. The student size in a class does not change, no matter what the grouping is. It doesn't make sense to have some students with no sweets in hand after a distribution, ie. ALL students must have sweets in hand after each distribution.
Thus we can postulate that for all physical items involved in the grouping, the implied assumption holds, ie. All of the physical items must be used after each distribution.
Seen in this light, then we have a very clear guideline on when to use the Gap and Difference method and the answer provided by the Gap and Difference method is the only possible answer.
Let me explain the thought process in me when I read the question.
The first question that I have was \" why is there a remainder of 15 and not a number less than 4 when 4 sweets were packed? why not 11, or 7 for eg \" and then it became clear to me that there was a fixed number of packets and for each scenario, all the packets were used. If there were more than enough packets, then the question is why not fill up 5 packets with 4 sweets each with a remainder of 7 sweets - this would yield a minimum number of 27 as well.
So, for question like this, I would suggest that if the student is unsure, it is best to use the Listing method and then reason and state that all packets were used.
cheers. -
can someone help me on this please
jerry bought some posters. he bought 3x as many pcs of poster A as poster C and 2x as many pcs of poster B as poster C. he spent a total of $300 on the posters
poster A $1.50 poster B $3.00 poster C $4.50
a] how many pcs of poster B did he buy
b] how much more did he spend on poster B than on poster A -
raysusan:
A [][][]can someone help me on this please
jerry bought some posters. he bought 3x as many pcs of poster A as poster C and 2x as many pcs of poster B as poster C. he spent a total of $300 on the posters
a] how many pcs of poster B did he buy
b] how much more did he spend on poster B than on poster A
B [][]
C []
6 Units = $300
1 Unit = 300/6= $50
So 2 pcs of poster B; $50 more on poster B than A.
but then again, can the following be possible too?
A [][][][][][][][][][][][][][][]
B [][][][][][][][][][]
C [][][][][]
30 Units = $300
1 Unit = 300/30= $10
Diff btwn B and A=5 Units=5x$50
So 10pcs of poster B; $50 more on poster B thank A.
:imdrowning: -
teh_oh:
that is not the answer
A [][][]raysusan:
can someone help me on this please
jerry bought some posters. he bought 3x as many pcs of poster A as poster C and 2x as many pcs of poster B as poster C. he spent a total of $300 on the posters
a] how many pcs of poster B did he buy
b] how much more did he spend on poster B than on poster A
B [][]
C []
6 Units = $300
1 Unit = 300/6= $50
So 2 pcs of poster B; $50 more on poster B than A.
but then again, can the following be possible too?
A [][][][][][][][][][][][][][][]
B [][][][][][][][][][]
C [][][][][]
30 Units = $300
1 Unit = 300/30= $10
Diff btwn B and A=5 Units=5x$50
So 10pcs of poster B; $50 more on poster B thank A.
:imdrowning:
:imdrowning:
-
raysusan:
Hican someone help me on this please
jerry bought some posters. he bought 3x as many pcs of poster A as poster C and 2x as many pcs of poster B as poster C. he spent a total of $300 on the posters
a] how many pcs of poster B did he buy
b] how much more did he spend on poster B than on poster A
I am wondering if there is missing information such as the price of posters in the question.
In order to find out the number of poster B, I think we need to know the per unit cost of the poster.
Best wishes -
tianzhu:
sorry my bad
Hiraysusan:
can someone help me on this please
jerry bought some posters. he bought 3x as many pcs of poster A as poster C and 2x as many pcs of poster B as poster C. he spent a total of $300 on the posters
a] how many pcs of poster B did he buy
b] how much more did he spend on poster B than on poster A
I am wondering if there is missing information such as the price of posters in the question.
In order to find out the number of poster B, I think we need to know the per unit cost of the poster.
Best wishes
post edited
poster A $1.50 poster B $3.00 poster C $4.50 -
raysusan:
Hican someone help me on this please
jerry bought some posters. he bought 3x as many pcs of poster A as poster C and 2x as many pcs of poster B as poster C. he spent a total of $300 on the posters
poster A $1.50 poster B $3.00 poster C $4.50
a] how many pcs of poster B did he buy
b] how much more did he spend on poster B than on poster A
One way to solve this question is to use “Grouping”
Consider a group of 3 poster A, 2 poster B and 1 poster C.
3x1.5 --------4.5
2x3 ------- 6
1x4.5 ------ 4.5
Cost for 1 group ------- 15
300/15 ------- 20
There are 20 groups.
Hence, you’ll have
Poster A ------- 60
Poster B ------- 40
Poster C ------- 20
(40x3) – (60x1.5) ------- 30
Best wishes -
Hi ksi,
Thanks for the solution. -
wahwah:
:welcome:Hi ksi,
Thanks for the solution.
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