Q&A - PSLE Math

Academic support for Primary 6 and PSLE
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lizawa
BrownBelt
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Post by lizawa » Tue Sep 23, 2008 8:41 am

youngmum wrote:Thanks ks2me. I'll slowly digest and see if i can catch the ball. *kiss*
Yes, ks2me's explanation is correct. It's just converting % to fractions. You can show your child the solution and see if he understands. The kids are so trained to using models to solve such questions, sometimes, you just need to help them to start with the correct model, and they can "see" the solution.

Sarah
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P5 Math

Post by Sarah » Tue Sep 23, 2008 5:45 pm

thanks Chief for the working.

Need help for the following $ questions.

Question 1
the ration of $2 notes to 50-cent coins in Mabel's piggy bank was 13:8. She exchanged 24 pieces of $2 notes for some 50-cent coins, after which, the ratio of $2 notes to 50-cent coins became 1:8. What was the total value of $2 notes and 50-cent coins in the piggy bank at first?

Question 2
the ration of $5 notes to 20-cent coins in Mr Tan/ counter was 19:5. Mr Tan exchanged 15 of his $5 notes for some 20-cent coins. The ratio of the $5 notes to 20-cent coins then became 1:5. What was the total value of $5 notes and 20-cent coins at first?

Question 3
a box contained 50-cent coins and 20-cent coins in the ratio of 2:3. Peter took out four 50-cent coins, exchanged them for 20-cents and put the money back into the box. The ratio then became 2:7. Find the sum of money in the box at first.

thanks for helping, exam is coming, u know.

Priskhipo
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Post by Priskhipo » Tue Sep 23, 2008 10:21 pm

HI Sarah,

The 3 questions share similar strategy.

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youngmum
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Post by youngmum » Thu Sep 25, 2008 6:25 pm

For the above question 1 - for step 1 why 12 + 24? I don't understand the first step, the rest ok. Pls explain to me. Thanks.

i solved it the ratio way though.

13: 8 = 39 : 24
1:8 = 15:120

So, 39 x 2 = 78
24/2 = 12

total = 78 + 12 = 90
Last edited by youngmum on Fri Sep 26, 2008 10:01 am, edited 3 times in total.

ChiefKiasu
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Post by ChiefKiasu » Thu Sep 25, 2008 7:12 pm

Priskhipo wrote:HI Sarah,

The 3 questions share similar strategy.
...
Priskhipo, thanks for the detailed "workout"!


heutistmeintag
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Post by heutistmeintag » Thu Sep 25, 2008 9:17 pm

Priskhipo, may I know if you are a teacher or tuition teacher? Your answers are so professional. Do you take students? :) :wink:

lantian
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Post by lantian » Fri Sep 26, 2008 12:17 am

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Priskhipo
YellowBelt
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Post by Priskhipo » Fri Sep 26, 2008 8:32 pm

heutistmeintag wrote:Priskhipo, may I know if you are a teacher or tuition teacher? Your answers are so professional. Do you take students? :) :wink:
Hi heutistmeintag,

Thanks you. I'm a teacher but not in the mainstream kind.
Sorry, I'm not taking in any students for tuition.
I'm glad to be able to help out in this website and continue to do so if time permit. :)

Priskhipo
YellowBelt
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Post by Priskhipo » Fri Sep 26, 2008 8:43 pm

youngmum wrote:For the above question 1 - for step 1 why 12 + 24? I don't understand the first step, the rest ok. Pls explain to me. Thanks.

i solved it the ratio way though.

13: 8 = 39 : 24
1:8 = 15:120

So, 39 x 2 = 78
24/2 = 12

total = 78 + 12 = 90

Compare the orange bar (13 small units) to the bar consists of blue rectange (1 small unit) with green and white dotted-line rectangles.

The difference is indicated by the arrow (12 units).
The green rectangle represents 12 number and the white dotted-line rectangle represents 24 number.

Therefore 12 units represent 12 + 24 = 36

lantian
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Re: P5 Math

Post by lantian » Mon Sep 29, 2008 2:51 pm

Sarah wrote: Q2. A, B and C are three numbers. The average a, B and C is 5 greater tha the averaga of A and b. If C is 38, find the total of A, B and C.
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