Q&A - PSLE Math

[tianzhu]

Lynn2:

Hi Tianzhu,


Thanks for the explanation.I will try to explain to dd .Can u help another similar question?

5 There were twice as many fifty cent coins as twenty cent coins in a coin box.Stephanie added in some ten cent coins into the coin box and the total amount became $11.30.If there were 9 more ten cent coins than twenty cent coins, how many coins of each type were in the coin box?

Hi

You may use MD or Number*Value Method to solve this question.

I’ll use the second method for this solution. It’s preferable to present it in tabulated form. Due to time constraints,I’ll not do it using PowerPoint.

Fifty cents coins ----- 2 units*50 ------- 100units
Twenty cent coins -----1 unit*20 ------ 20 units
Ten cent coins ----- 1 unit*10 ----- 10 units
Total ------130 units

9 ten cent coins ------ 90 cents
1130 – 90 ----- 1040

1040/130 ----- 8

The number of coins are as follows

Fifty cents coins ----- 2*8 ----- 16
Twenty cent coins -----1*8 ------ 8
Ten cent coins ----- (8+9) ----- 17

Best wishes

[Lynn2]

Hi Tianzhu,


Thanks.

This one I think we will use model to solve it.I am still trying hard to explain the earlier coin questions, still cannot see the picture...sigh...


cheers
Lynn2

tianzhu:

Lynn2:

Hi Tianzhu,

Thanks for the explanation.I will try to explain to dd .Can u help another similar question?

5 There were twice as many fifty cent coins as twenty cent coins in a coin box.Stephanie added in some ten cent coins into the coin box and the total amount became $11.30.If there were 9 more ten cent coins than twenty cent coins, how many coins of each type were in the coin box?

Hi

You may use MD or Number*Value Method to solve this question.

I’ll use the second method for this solution. It’s preferable to present it in tabulated form. Due to time constraints,I’ll not do it using PowerPoint.

Fifty cents coins ----- 2 units*50 ------- 100units
Twenty cent coins -----1 unit*20 ------ 20 units
Ten cent coins ----- 1 unit*10 ----- 10 units
Total ------130 units

9 ten cent coins ------ 90 cents
1130 – 90 ----- 1040

1040/130 ----- 8

The number of coins are as follows

Fifty cents coins ----- 2*8 ----- 16
Twenty cent coins -----1*8 ------ 8
Ten cent coins ----- (8+9) ----- 17

Best wishes

[tianzhu]

Lynn2:

This one I think we will use model to solve it.I am still trying hard to explain the earlier coin questions, still cannot see the picture...sigh...

Hi

Don’t worry too much now.

I am in a hurry now, so cannot do the solution using PowerPoint.
I’ll do it at a later time.

Enjoy your dinner first.

Best wishes

[Belle2011]

Lynn2:

Box A contains 50 cent coins and Box B contains $1 coins.Box A contains 17 more coins than Box B.The amount of money in Box A is $15.50 less than in Box B.Find the total amount of money in the boxes


Cheers
Lynn2

I use model:

A: [] + 17*0.5
B: [] + [] where [] is number of 50cts coins * 0.50

Since B-A is 15.5,
[] is 17*0.5 + 15.5 = 24.
Number of 50cts coins = 24/0.5 = 48.

Thus there are 48+17 = 65 of 50cts coins.

Is the above correct?

Thank-you.

Cheers,
Belle.

[Hifive]

tianzhu:

Hifive:

Karen made 120 more cookies than apple pies. After selling one third of the cookies and 25% of the apple pies, she had 70 more apple pies than cookies. What is the total number of cookies and apple pies that Karen made?

Hi

You may use MD to solve this question.

Some quick pointers for the MD.If needed, I’ll draw out the MD at a later time.

Cookies ----- 12 units + 120
Apple pies ------ 12 units

Cookies sold ------- 4 units + 40
Apple pies sold ------- 3 units

Cookies left ------ 8 units + 80
Apple pies left ------- 9 units

9 units ------- 8 units + 80 + 70
1 unit ------- 150

24 units -------- 3600
Total number -------- 3600+120 -------3720

Best wishes

Hi Tianzhu

Thanks for the explanation! Your explanation is very clear and I can manage with the models on my own. Thanks for your help!

[MathIzzzFun]

Lynn2:

Hi Tianzhu,


Thanks for the explanation.I will try to explain to dd .Can u help another similar question?

5 There were twice as many fifty cent coins as twenty cent coins in a coin box.Stephanie added in some ten cent coins into the coin box and the total amount became $11.30.If there were 9 more ten cent coins than twenty cent coins, how many coins of each type were in the coin box?

Thanks and good day.

Lynn2

tianzhu:

[quote=\"Lynn2\"]Box A contains 50 cent coins and Box B contains $1 coins.Box A contains 17 more coins than Box B.The amount of money in Box A is $15.50 less than in Box B.Find the total amount of money in the boxes

Hi

Assume or pretend that the number of coins in Box B is equal to that of Box A

17*1 ------ 17
17 + 15.5 ------- 32.5

Difference between $1 and 50 cents -------50 cents

3250/50 ------65 50 cents coins

Hence, 48 $1 coins

48 + 32.50 -------- 80.50

Best wishes

[/quote]Hi Lynn2

Hope this will help.


http://postimage.org/image/drdoc9wk/

cheers.

[ozora]

MathIzzzFun:

ozora:

[quote=\"MathIzzzFun\"]
Hi ozora,

Aaron had 8 units + 8, so 1/8 = 1/8 of 8 units + 1/8 of 8 = 1 unit + 1

cheers

[/quote]oic
thanks

[tianzhu]

Hifive:

Hi Tianzhu

Thanks for the explanation! Your explanation is very clear and I can manage with the models on my own. Thanks for your help!

Hi

You're welcome.

Best wishes

[tianzhu]

Belle2011:

Is the above correct?

Hi Belle

You are on the right track.

You have to convert to value of money for the answer.

Best wishes

[Lynn2]

Hi MathIzzzFun



Thanks, I will show it to dd to see she can understand.

This kind of coins questions has been stuck in her since pri five, no matter how I try to explain to date, still cannot clear.Other topics, all can clear, cos she understand.
In the recent exam, she has to do 18 times of guess and check just to get the answer.I think its quite a waste of time tho she eventually gets the answer.


Cheers


Hi Tianzhu,

Thanks for the explanation.I will try to explain to dd .Can u help another similar question?

5 There were twice as many fifty cent coins as twenty cent coins in a coin box.Stephanie added in some ten cent coins into the coin box and the total amount became $11.30.If there were 9 more ten cent coins than twenty cent coins, how many coins of each type were in the coin box?

Thanks and good day.

Lynn2

tianzhu:

Lynn2:

Box A contains 50 cent coins and Box B contains $1 coins.Box A contains 17 more coins than Box B.The amount of money in Box A is $15.50 less than in Box B.Find the total amount of money in the boxes

Hi

Assume or pretend that the number of coins in Box B is equal to that of Box A

17*1 ------ 17
17 + 15.5 ------- 32.5

Difference between $1 and 50 cents -------50 cents

3250/50 ------65 50 cents coins

Hence, 48 $1 coins

48 + 32.50 -------- 80.50

Best wishes

[/quote]

Hi Lynn2

Hope this will help.


http://postimage.org/image/drdoc9wk/

cheers.[/quote]