Q&A - P5 Math

[cimman]

whywhy:

Hi Tianzhu, i need a simple method to do this St nick SA1 Q13.

Song Ren had a total of 50 coins. The coins were in denominations of 50ct, 20ct, & 5ct. He had an equal number of 50ct coins as 20ct coins. The total value of the 20ct coins & 5ct coins was $4.10. How many coins of each denomination did Song Ren have?

this is one of those problem sums where algebra provides a simple solution.
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[sherlynDD]

http://i47.tinypic.com/w05fzo.jpg\">


Can anyone help to solve? Thanks!

[tianzhu]

sherlynDD:

http://i47.tinypic.com/w05fzo.jpg\">


Can anyone help to solve? Thanks!

Hi

Where is this question from?

Slide triangle ABC until AT meets DV (no more overlapping)

Area of shaded area ------ 8*6 – (1/2*6*1.5) ------- 43.5

Another way

6*5 ------ 30

½*6*3 ------ 9

½*3*3 ------ 4.5

Total ------- 43.5

Best wishes

[sherlynDD]

tianzhu:

sherlynDD:

http://i47.tinypic.com/w05fzo.jpg\">


Can anyone help to solve? Thanks!

Hi

Where is this question from?

Slide triangle ABC until AT meets DV (no more overlapping)

Area of shaded area ------ 8*6 – (1/2*6*1.5) ------- 43.5

Another way

6*5 ------ 30

½*6*3 ------ 9

½*3*3 ------ 4.5

Total ------- 43.5

Best wishes

Hi tianzhu,

Thank you! This qn is from Nangyang CA2 2011.
The slide method is quite cool, but not easy to find out immediately.
The second way, I can not see how 6*5 come from. Thanks.

[tianzhu]

sherlynDD:

Best wishes

Hi tianzhu,

Thank you! This qn is from Nangyang CA2 2011.
The slide method is quite cool, but not easy to find out immediately.
The second way, I can not see how 6*5 come from. Thanks.[/quote]
Hi

You're welcome.

This is not an easy question for P5 kids.

8 - 3 ----- 5

From point S, extend a horizontal line to meet line DV, you'll see a rectangle of 6*5

Best wishes

[whywhy]

Thanks to Tianzhu. thanks to Cimman for the contribution. Is your algebra method taught in sch n acceptable by psle marker?

[despmom99]

whywhy:

Thanks to Tianzhu. thanks to Cimman for the contribution. Is your algebra method taught in sch n acceptable by psle marker?

Hi, whywhy

My child's tutor who is an ex-Math HOD is using this table method too. My child was revising the concept taught the other day. Think she gave a name to the concept. I check and let you know. I was quite concerned if this method was acceptable by psle marker and asked the tutor. She said yes. She was supervisor of some sort during the psle marking so I trust her.

[YumYum]

Hi, can anyone pls help with this Qn:


1. A seamstress had some white and black buttons. 60% of the buttons were white. She bought an additional 120 buttons. Now the percentage of white buttons became 40% of the total. How many white buttons did he have at first?


2. The ratio of the number of ten cent to twenty cent stamps in an album was 3:4. 50 ten-cent stamps were taken out, exchanged for twenty cent stamps of the same value and put back into the album. The ratio became 1:5. Find the total value of all the stamps in the album at first.

thanks

[tianzhu]

YumYum:

Hi, can anyone pls help with this Qn:


1. A seamstress had some white and black buttons. 60% of the buttons were white. She bought an additional 120 buttons. Now the percentage of white buttons became 40% of the total. How many white buttons did he have at first?

Hi

Q1 has been discussed before.

Please refer to page 209 of this thread.

http://www.kiasuparents.com/kiasu/forum/viewtopic.php?f=69&t=280&start=2080

Best wishes

[tianzhu]

YumYum:

2. The ratio of the number of ten cent to twenty cent stamps in an album was 3:4. 50 ten-cent stamps were taken out, exchanged for twenty cent stamps of the same value and put back into the album. The ratio became 1:5. Find the total value of all the stamps in the album at first.

Hi

One possible way

At first

ten cents stamps: twenty cent stamps ------ 3u:4u

50 ten-cent stamps were taken out, exchanged for twenty cent stamps of the same value and put back into the album.

50 ten-cent stamps ------- 25 twenty cent stamps

Change

ten cents stamps: twenty cent stamps ------ -50:+25

In the end

ten cents stamps: twenty cent stamps ------ 1p:5p

Equalise the parts.

3u – 50 ------ 1p
(x5)
15u – 250 ------ 5p

4u + 25 ------ 5p

15u – 250 ------- 4u + 25

11u ------ 275

1u ------- 25

Total value of all the stamps in the album at first

ten cents stamps: twenty cent stamps ------ (3*25)*10cents : (4*25)*20cents ------- $27.50

Best wishes