Q&A - PSLE Math

[MathIzzzFun]

ozora:

need some help in these question.

Jean had some stamps. She gave Kay 1/3 of her stamps plus 6 more. she gave Liz 1/3 of her remaining stamps plus 4 more. If Jean finally had half as many stamps as Liz, how many stamps did Kay receive? my answer is 15.
Besides model drawing, how to use unitary method to solve?
is it similiar to http://www.kiasuparents.com/kiasu/forum/viewtopic.php?f=69&t=280&start=8620?

\"Kay\" was missing in the question - I have inserted as shown in blue above.

Jean --> 9 units
Kay --> 3 units + 6
Remainder --> 6 units - 6

Liz --> 2 units - 2 + 4 = 2 units + 2
Jean --> 4 units -4 - 4 = 4 units - 8
Jean had half as many as Liz
8 units - 16 = 2 units + 2
6 units --> 18, 1 unit --> 3

Kay --> 15
cheers.

[Easy-going]

Hi

My son has this difficult question. I hope someone can help us.

Qn 32 Alfred and Benedict were given some money each. If Alfred spent $45 each week and Benedict spent $90 each week, Alfred would still have $840 left when Benedict spent all his money. If Alfred spent $90 each week and Benedict spent $45 each week, Alfred would still have $210 left when Benedict had spent all his money.
a) How much money did Alfred receive?
b) How much money did Benedict receive?

Thanks in advance.

[smileplease]

Need help, i need Unitary Method solution. Thanks.


Lena and Terry shared a sum of money. Lena’s share was $180 less than Terry’s share.
After Terry gave 1/7 of his share to Lena, Lena had $20 more than Terry.
How much did Lena have at first?

[MathIzzzFun]

smileplease:

Need help, i need Unitary Method solution. Thanks.


Lena and Terry shared a sum of money. Lena's share was $180 less than Terry's share.
After Terry gave 1/7 of his share to Lena, Lena had $20 more than Terry.
How much did Lena have at first?

In the end,
Terry --> 6 units
Lena --> 6 units + $20

At first,
Terry --> 7 units
Lena --> 5 units + $20
Terry had $180 more than Lena,
7 units = 5 units + $20 + $180
1 unit --> $100

At first, Lena --> $520

cheers.

[MathIzzzFun]

Easy-going:

Hi

My son has this difficult question. I hope someone can help us.

Qn 32 Alfred and Benedict were given some money each. If Alfred spent $45 each week and Benedict spent $90 each week, Alfred would still have $840 left when Benedict spent all his money. If Alfred spent $90 each week and Benedict spent $45 each week, Alfred would still have $210 left when Benedict had spent all his money.
a) How much money did Alfred receive?
b) How much money did Benedict receive?

Thanks in advance.

This was discussed on pg 856 -
http://www.kiasuparents.com/kiasu/forum/viewtopic.php?f=69&t=280&p=942633&hilit=4%20approaches#p942633

cheers

[mathnoobs]

I was going through some old posts and saw this problem which I'm very confused on what it means:


Siti had some money. She gave some money to Kelly and Lindy and saved the rest. The ratio of her savings to the amount she gave away was 5: 8. The ratio of Kelly's money to Lindy's money was 5: 3 at first. After Kelly's money increased by $128 and Lindy's money decreased by $128, the ratio of Kelly's money to Lindy's money became 3: 1. How much money did Siti save?

Mathizzfun, you've provided a solution in http://www.kiasuparents.com/kiasu/forum/viewtopic.php?f=68&t=25129&start=1240
However, I don't quite understand the solution.
Siti's savings : Kelly's money : Lindy's money
--> 5u: 5u : 3u

I understood that:
Siti's original sum of money(Before) - money given to Kelly and Lindy = Siti's savings (After)
Thus Siti's Savings (After) = 5u
Money given to Kelly and Lindy = 8u
Siti's original sum of money (Before) = 13u
Based on this, I don't quite understand how you equate 5u:5u:3u.
There seems to be no relationship between Siti's 5u (After) and Kelly:Lindy ratio (5:3) (Before)

I also have a query on this part:
Kelly's money : Lindy's money --> 5u + $128 : 3u - $128 = 3 : 1
From the question, it seems that Kelly's money (After) = 5u + 128 + amt given by Siti
and Lindy's money (After) = 3u - 128 + amt given by Siti
what happened to the amount given by Siti ? :?

[MathIzzzFun]

mathnoobs:

I was going through some old posts and saw this problem which I'm very confused on what it means:


Siti had some money. She gave some money to Kelly and Lindy and saved the rest. The ratio of her savings to the amount she gave away was 5: 8. The ratio of Kelly's money to Lindy's money was 5: 3 at first. After Kelly's money increased by $128 and Lindy's money decreased by $128, the ratio of Kelly's money to Lindy's money became 3: 1. How much money did Siti save?

Mathizzfun, you've provided a solution in http://www.kiasuparents.com/kiasu/forum/viewtopic.php?f=68&t=25129&start=1240
However, I don't quite understand the solution.
Siti's savings : Kelly's money : Lindy's money
--> 5u: 5u : 3u

I understood that:
Siti's original sum of money(Before) - money given to Kelly and Lindy = Siti's savings (After)
Thus Siti's Savings (After) = 5u
Money given to Kelly and Lindy = 8u
Siti's original sum of money (Before) = 13u
Based on this, I don't quite understand how you equate 5u:5u:3u.
There seems to be no relationship between Siti's 5u (After) and Kelly:Lindy ratio (5:3) (Before)

I also have a query on this part:
Kelly's money : Lindy's money --> 5u + $128 : 3u - $128 = 3 : 1
From the question, it seems that Kelly's money (After) = 5u + 128 + amt given by Siti
and Lindy's money (After) = 3u - 128 + amt given by Siti
what happened to the amount given by Siti ? :?

My interpretation of the question is:

http://i49.tinypic.com/15hledl.png\">

cheers.

[ftwm]

2/5 of my sister’s beads are yellow. 7/13 of the remaining beads are green. The rest of the beads are black. If there are 32 more yellow beads than black beads, how many beads are green?

[MathIzzzFun]

ftwm:

2/5 of my sister's beads are yellow. 7/13 of the remaining beads are green. The rest of the beads are black. If there are 32 more yellow beads than black beads, how many beads are green?

Remainder --> 3/5 of beads

Green --> 7/13 x 3/5 of beads = 21/65 of beads
Black --> 6/13 x 3/5 of beads = 18/65 of beads
Yellow --> 2/5 of beads = 26/65 of beads

26/65 - 18/65 = 8/65
8/65 of beads --> 32
21/65 of beads --> 84

There are 84 green beads

cheers.

[speedmaths.012624com]

ftwm:

2/5 of my sister's beads are yellow. 7/13 of the remaining beads are green. The rest of the beads are black. If there are 32 more yellow beads than black beads, how many beads are green?

Hi ftwm,

One possible method:

Look at the denominators; 5 and 13.
The denominators are your friends.

5 x 13 = 65

Let there be 65 boxes of beads

2/5 of my sister's beads are yellow
2/5 x 65 = 26
26 boxes contain yellow beads

Remaining = 65 - 26 = 39 boxes

7/13 of the remaining beads are green
7/13 x 39 = 21
21 boxes contain green beads

Remaining = 39 - 21 = 18 boxes
18 boxes contain black beads

26 boxes contain yellow beads
18 boxes contain black beads

There are 26 - 18 = 8 more boxes of yellow than black beads
there are 32 more yellow beads than black beads

8 boxes contain 32 beads

1 box contains ??? beads

Can you work from here?

Cheers


speedmaths.com