Q&A - P5 Math
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MathIzzzFun:
I'm not sure if your interpretation is correct since I'm confused with the interpretation myself. However, the model answer seems wrong.
I interpret the question as:mathnoobs:
this question looks like an Unchanged Total problem to me. But I'm stumped by the +4 girls.
In a class, the number of boys left was replaced by the same number of girls. At first boys is 2/3 of girls. In the end, boys is 3/5 of girls + 4 girls. Find the number of pupils in the class at first ? Ans: 100 pupils
In a class, the number of boys who left the class was replaced by same number of girls. At first, the number of boys was 2/3 the number of girls. In the end, the number of boys is 4 more than 3/5 the number of girls. Find the number of pupils in the class at first ?
is this correct ? If it is, there are multiple answers and the minimum number of pupils = 140. If there are 100 pupils the number of girls at first is equal to the number of girls in the end, which is incorrect.
cheers.
The model answer was:
At first: Boy: Girl -> 2:3
At End: Boy: Girl -> 3:5 + 4 girls
At First: 2/3 x 5x5 = 10/15
At End: (3/5 + 4 girls ) x 3/3 = 9/15 + 4 girls
10 units = 9 units + 4 girls
1 unit = 4 girls/pupil
Total Pupils = (10 units + 15 units) x 4 pupils = 100 -
mathnoobs:
is this an exam question ? could you post the original question?
I'm not sure if your interpretation is correct since I'm confused with the interpretation myself. However, the model answer seems wrong.MathIzzzFun:
this question looks like an Unchanged Total problem to me. But I'm stumped by the +4 girls.
In a class, the number of boys left was replaced by the same number of girls. At first boys is 2/3 of girls. In the end, boys is 3/5 of girls + 4 girls. Find the number of pupils in the class at first ? Ans: 100 pupils
I interpret the question as:
In a class, the number of boys who left the class was replaced by same number of girls. At first, the number of boys was 2/3 the number of girls. In the end, the number of boys is 4 more than 3/5 the number of girls. Find the number of pupils in the class at first ?
is this correct ? If it is, there are multiple answers and the minimum number of pupils = 140. If there are 100 pupils the number of girls at first is equal to the number of girls in the end, which is incorrect.
cheers.
The model answer was:
At first: Boy: Girl -> 2:3
At End: Boy: Girl -> 3:5 + 4 girls
At First: 2/3 x 5x5 = 10/15
At End: (3/5 + 4 girls ) x 3/3 = 9/15 + 4 girls
10 units = 9 units + 4 girls
1 unit = 4 girls/pupil
Total Pupils = (10 units + 15 units) x 4 pupils = 100
cheers. -
mathnoobs:
Hithis question looks like an Unchanged Total problem to me. But I'm stumped by the +4 girls.
In a class, the number of boys left was replaced by the same number of girls. At first boys is 2/3 of girls. In the end, boys is 3/5 of girls + 4 girls. Find the number of pupils in the class at first ? Ans: 100 pupils
Where is this question from?
At first boys is 2/3 of girls.
Boys:Girls ------- 2:3 ------ 10:15
The number of boys left was replaced by the same number of girls. In the end, boys is 3/5 of girls + 4 girls.
Boys:Girls ------- 3:5 + 4 girls -------9:15 + 4 girls
10 u ā 4 ------- 9u
1u ------- 4
Number of pupils@first ------- 25*4 ------- 100
Best wishes -
tianzhu:
it's a problem that came from a friend, so I don't know it's origins. It is the full question, I've not edited it in anyway.
Himathnoobs:
this question looks like an Unchanged Total problem to me. But I'm stumped by the +4 girls.
In a class, the number of boys left was replaced by the same number of girls. At first boys is 2/3 of girls. In the end, boys is 3/5 of girls + 4 girls. Find the number of pupils in the class at first ? Ans: 100 pupils
Where is this question from?
At first boys is 2/3 of girls.
Boys:Girls ------- 2:3 ------ 10:15
The number of boys left was replaced by the same number of girls. In the end, boys is 3/5 of girls + 4 girls.
Boys:Girls ------- 3:5 + 4 girls -------9:15 + 4 girls
10 u ā 4 ------- 9u
1u ------- 4
Number of pupils@first ------- 25*4 ------- 100
Best wishes
The problem I have though is:
10u - 4 = 9u
I don't see how the 4 fits in there.
What does 3/5 of girls + 4 girls mean ? -
mathnoobs:
Hi
The problem I have though is:
10u - 4 = 9u
I don't see how the 4 fits in there.
What does 3/5 of girls + 4 girls mean ?
Based on the given answer of 100 pupils, we can say that the number of girls added to the class is 4.The number of boys being replaced is also 4.
Best wishes![](\"http://farm9.staticflickr.com/8311/8028173647_e8bac2a7f9_z.jpg\")
http://farm9.staticflickr.com/8311/8028173647_e8bac2a7f9_z.jpg\">
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mathnoobs:
it's a problem that came from a friend, so I don't know it's origins. It is the full question, I've not edited it in anyway.
Hitianzhu:
[quote=\"mathnoobs\"]this question looks like an Unchanged Total problem to me. But I'm stumped by the +4 girls.
In a class, the number of boys left was replaced by the same number of girls. At first boys is 2/3 of girls. In the end, boys is 3/5 of girls + 4 girls. Find the number of pupils in the class at first ? Ans: 100 pupils
Where is this question from?
At first boys is 2/3 of girls.
Boys:Girls ------- 2:3 ------ 10:15
The number of boys left was replaced by the same number of girls. In the end, boys is 3/5 of girls + 4 girls.
Boys:Girls ------- 3:5 + 4 girls -------9:15 + 4 girls
10 u ā 4 ------- 9u
1u ------- 4
Number of pupils@first ------- 25*4 ------- 100
Best wishes
The problem I have though is:
10u - 4 = 9u
I don't see how the 4 fits in there.
What does 3/5 of girls + 4 girls mean ?[/quote]\"In the end, boys is 3/5 of girls + 4 girls\" could mean :
1) there are 4 more girls in the end, and the number of boys is 3/5 the number of girls --> in this case, the answer is 160 pupils
2) the number of boys is 4 more than 3/5 the number of girls --> in the case, there are multiple answers, the minimum number of pupils is 140
3) the number of boys is 3/5 the original number of girls and there are 4 more girls in the end --> solution as in tianzhu post
cheers. -
MathIzzzFun:
thank you for your explanation, MathIzzfun. It makes sense now.
\"In the end, boys is 3/5 of girls + 4 girls\" could mean :
1) there are 4 more girls in the end, and the number of boys is 3/5 the number of girls --> in this case, the answer is 160 pupils
2) the number of boys is 4 more than 3/5 the number of girls --> in the case, there are multiple answers, the minimum number of pupils is 140
3) the number of boys is 3/5 the original number of girls and there are 4 more girls in the end --> solution as in tianzhu post
cheers. -
tianzhu:
thank you for the detail graphics Tianzhu. :thankyou:
Himathnoobs:
The problem I have though is:
10u - 4 = 9u
I don't see how the 4 fits in there.
What does 3/5 of girls + 4 girls mean ?
Based on the given answer of 100 pupils, we can say that the number of girls added to the class is 4.The number of boys being replaced is also 4.
Best wishes -
Molly had some flour. She used an equal amount of flour daily to bake cakes. After 15 days, she had 3/8 of the flour left. After another 3 days, she had 3 3/4 of flour left. How much flour did she use in 12 days?
pls assist. tq. -
hi need help in this Q.
1/5 of a rectangular tank measuring 30cm long, 20cm wide and 10cm high was filled with water. The ratio of the volume of the water in the tank to that in a bottle was 4 : 3. When some water was poured out of the bottle into the tank, the ratio of the new volume of water in the tank to that in the bottle was 2 : 1. How much water had been poured out of the bottle?
Tq.
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