Q&A - PSLE Math

Academic support for Primary 6 and PSLE
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ChiefKiasu
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Post by ChiefKiasu » Tue Sep 16, 2008 3:19 pm

youngmum wrote:(1) Mrs Tan has some pencils. If she packs them into bundles of 5 pencils in each bundles, she will have 4 extra pencils. If she packs them into bundles of 9 pencils in each bundles, she will need 7 mor epencils. How many pencils are there?
Standard guess and check question (Level P3)
Bundles of 5: 9, 14, 19, 24, 29, 34, 39, 44, 49, 54, 59, 64, 69, 74
Bundles of 9: 2, 11, 20, 29, 38, 47, 56, 65, 74
Answer: Total number of pencils = 74

Correction: The better answer is 29, although 74 is another possible answer.
youngmum wrote:(2) At a bk fair, Tom spent $6 less than of his money on a storybook and $2 more than of his remaining money on reference books. After buying thebooks, he still had $10 left.

(a) How much money was left after he bought his story books and before hte bought the reference bk?
(b) How much money did Tom have at first?
Sorry... catch no ball... less than WHAT?... more than WHAT?... the question has my logic circuits tied up in knots. Need someone to untie them for me :?
youngmum wrote:(3) There were 2 identica flights of steps. For the first flights of steps, Siti walked up some steps adn ran 4 steps and took a total of 75 seconds. For the second flight of steps, she walked up some steps and ran 11 steps and took a total of 40 seconds. how long will siti take if she had walked up both flight of steps? Leave your answer in seconds.
Assuming Siti walked and ran at the same constant speeds:
Time difference in running up (11-4) 7 steps = 75-40 = 35s
So additional time taken to walk up 1 step = 35/7 = 5s
Additional time taken to walk up 4 steps = 4x5 = 20s
Total time taken to walk up 2 flights of steps
= 2 x (20+75) = 190
or = 2 x (11x5 + 40) = 190
Last edited by ChiefKiasu on Tue Sep 16, 2008 10:51 pm, edited 1 time in total.

youngmum
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Post by youngmum » Tue Sep 16, 2008 3:32 pm

Wow, chief KS, thanks. Gosh i feel so stupid.

ChiefKiasu
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Post by ChiefKiasu » Tue Sep 16, 2008 3:40 pm

youngmum wrote:Wow, chief KS, thanks. Gosh i feel so stupid.
No no... we should not feel stupid... as kids, we ourselves were never exposed to such "brain twisters", and we taught to solve problems in the most efficient way possible. We were taught processes of solving instead of principles of understanding. That's why we find it so hard to adapt to the "new" math.

ChiefKiasu
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Post by ChiefKiasu » Tue Sep 16, 2008 5:06 pm

ChiefKiasu wrote:
youngmum wrote:(1) Mrs Tan has some pencils. If she packs them into bundles of 5 pencils in each bundles, she will have 4 extra pencils. If she packs them into bundles of 9 pencils in each bundles, she will need 7 mor epencils. How many pencils are there?
Standard guess and check question (Level P3)
Bundles of 5: 9, 14, 19, 24, 29, 34, 39, 44, 49, 54, 59, 64, 69, 74
Bundles of 9: 2, 11, 20, 29, 38, 47, 56, 65, 74
Answer: Total number of pencils = 74
...
Er... on closer examination, I think I overshot the smallest number that matches, which is 29 :oops: Guess I won't pass PSLE this year :cry:

lantian
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Post by lantian » Tue Sep 16, 2008 6:07 pm

youngmum wrote:How to solve these 3 questions pretty please?

(2) At a bk fair, Tom spent $6 less than of his money on a storybook and $2 more than of his remaining money on reference books. After buying thebooks, he still had $10 left.
(a) How much money was left after he bought his story books and before hte bought the reference bk?
(b) How much money did Tom have at first?
Hi youngmum
Just wonder whether or not there is missing info here.

Tom spent $6 less than of his money on a storybook
eg $6 less some fraction of his money


youngmum
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Post by youngmum » Tue Sep 16, 2008 6:37 pm

ChiefKiasu wrote: Er... on closer examination, I think I overshot the smallest number that matches, which is 29 :oops: Guess I won't pass PSLE this year :cry:
Oh good, if everyone is like you, then probably i won't fail too badly either. lol. Heng ar. Some1 just told me - you don't call yourself kiasu for nothing you know.:lol:
lantian wrote: ... Just wonder whether or not there is missing info here.

Tom spent $6 less than of his money on a storybook
eg $6 less some fraction of his money...
Oh, then i think the Q got an error then. If it really can't be solved then good lah. I don't feel so silly. lol. 8)

youngmum
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Post by youngmum » Wed Sep 17, 2008 12:51 pm

Another Question - OMG.

The average number of letters in 6 magic spells is 9. Four of the magic spells are LUMOS, CRUICIO, PROTEGO and CONFUNDO. The 2 remaining spells have the same number of letters. How many letters does each of teh 2 spells have?

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Post by Guest » Wed Sep 17, 2008 1:25 pm

youngmum wrote:Another Question - OMG.

The average number of letters in 6 magic spells is 9. Four of the magic spells are LUMOS, CRUICIO, PROTEGO and CONFUNDO. The 2 remaining spells have the same number of letters. How many letters does each of teh 2 spells have?


is there any error in any of the spells given, the number of letters? 27 letter is odd number so not divisible by 2 unless they accept 13.5 for each of the remaining spell with an "O" cut into half and form as letter "C" in each of the remaining spells?? LOL....

youngmum
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Post by youngmum » Wed Sep 17, 2008 1:52 pm

huh? no error leh. (other than 'the' spell wrongly lah). Hm. how ar. same alphabets counted as 1 time?

ChiefKiasu
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Post by ChiefKiasu » Wed Sep 17, 2008 6:18 pm

youngmum wrote:Another Question - OMG.

The average number of letters in 6 magic spells is 9. Four of the magic spells are LUMOS, CRUICIO, PROTEGO and CONFUNDO. The 2 remaining spells have the same number of letters. How many letters does each of teh 2 spells have?
It's also a test of your Harry Potter knowledge. The correct spelling for the unforgivable spell is CRUCIO, ie. 6 letters.

So total number of letters in the 4 spells = 26.
Total number of letters in the 6 spells = 9x6 =54
So total number of letters in the remaining 2 spells = 54-26 = 28
So each remaining spell has 28/2 = 14 letters each

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