
By: geniuskids (offline) Tuesday, April 30 2013 @ 09:54 AM CDT (Read 2686 times)



geniuskids 
Hi there, pls help solve Q16 and do enlighten if my answer for Q17 is correct.
As for Q8, I think question is wrongly set.... pls advise.
Q16. Kelly and Tom started walking from the same starting point but in opposite directions along a straight path. Kelly's average speed was 4km/h faster than Tom's. After walking for 3 hours, they were 40 km apart. What was Kelly's average speed.
Answer is 8 2/3
Q17. In a class library, there are some fiction and nonfiction books. If we remove 1 nonfiction book from the library, 1/7 of the remaining books are nonfiction books. If, instead of removing 1 nonfiction book, we remove 2 fiction books from thelibrary, then 1/5 of the remaining books are nonfiction books. How many books are there in the class library?
My answer is 15
But answer from answer sheet is 22.
Thanks

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Registered: 11/12/11 Posts: 169





By: echeewh (offline) Tuesday, April 30 2013 @ 09:06 PM CDT



echeewh 
Hey <Geniuskids>,
For Q8, are u referring to the ( Leon and Ken ) speed question? If yes, then this is similar to your Q16 and can be simpler, if not same.
Btw, your Q16, 17 dont come from NanHua 2012 SA1 paper? Or do they?
Following pls find my worked solutions:
Q16
Given that Kelly's (K) average speed was 4km/h faster than Tom's (T), K would travel an additional distance in this 3 hour duration.
Additional distance K travelled , D(K) = Additional Speed × Time
= 4 × 3 = 12 km
Since K and T were 40 km apart after this 3 hours,
D(T) = (40  12) ÷ 2 = 14 km {since total distance travelled by both K, T is 40 km }
D(K) = 14 + 12 = 26 km
Hence, Avg S (K) = D(K) ÷ T(K)
26 ÷ 3 = 8 2/3 km/h
=======
Q17
<1st IF>:
NF = 1p + 1
F = 6p
<2nd IF>:
NF = 1u
F = 4u + 2
In both instances, the number of NF and F books are the same.
Hence,
NF: 1p + 1 = 1u
F: 6p = 4u + 2
Rearranging these 2 equations, we have ...
1u  1p = 1  (1)
6p  4u = 2  (2)
Eliminating (u), multiply (1) 4x.
4u  4p = 4  (3)
(2)+(3):
6p  4p = 6
2p > 6
1p > 3
Total books = 7p + 1 {from <1st IF> }
7p + 1 > (7 × 3) + 1 = 22
=========
Trust the above helps.
Do let me know again if there's further clarification
Cheers,
Edward

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Registered: 04/21/11 Posts: 627





By: geniuskids (offline) Tuesday, April 30 2013 @ 09:54 PM CDT



geniuskids 
thank you Edward. You have been a great help in my journey without P6 Maths tuition in this era! Cheers
Yes Q8 is NanHua Paper 2 SA1 2012. There is a diagram on 2 stacks of blocks. Kindly refer.
I shall digest the other 2 questions soon.
Many thanks again!

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Registered: 11/12/11 Posts: 169





By: geniuskids (offline) Wednesday, May 01 2013 @ 05:05 AM CDT



geniuskids 
Hi Edward, I can't seem to understand Q17???

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By: echeewh (offline) Wednesday, May 01 2013 @ 11:29 PM CDT



echeewh 
Hi there,
Where in Q17 of my worked solution you do not understand? Appreciate that you elaborate further. (Or perhaps you really need to consider coming for my coaching class )
All the best,
Edward

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Registered: 04/21/11 Posts: 627





By: geniuskids (offline) Thursday, May 02 2013 @ 07:27 AM CDT



geniuskids 
Hi, at first i don't understand the simultaneous part....after clarifying with my friend, it rings a bell. thank you so much

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By: echeewh (offline) Thursday, May 02 2013 @ 07:57 PM CDT



echeewh 
Great ..
As to Q8 (with that 2 stacks of numbers), it really depends on the setter .
It can be a kinda heuristic question .. and my thoughts are as follows:
Remove 6 from Stack A, 16 from Stack B. Then the sums of the remaining 3 blocks in each stack will be the same (total 19). Do not put back the 'exchanged' blocks into the Stacks and you will get what the question wants.
Cheers,
Edward

Active Member
Registered: 04/21/11 Posts: 627





By: geniuskids (offline) Saturday, May 04 2013 @ 01:45 AM CDT



geniuskids 
Hi there.
Q8  The question says "exchanged one block from Stack A with one block from Stack B, i think it is not set properly.
Thanks

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Registered: 11/12/11 Posts: 169



