Q&A - P5 Math

[Superbugs]

Nanyang SA2 P2 Q16

Yili, Lynn and Devi went shopping. Yili spent 0.25 of the total amount Lynn and Devi spent, while Devi spent 4/11 of the total amount Yili and Lynn spent. Lynn spent $37.50 more than Yili. If Lynn had $90 before she went shopping, what fraction of her money did she spend? Express your answer in its simplest form.
Pls help

[Superbugs]

Appreciate it! This is so much easier! Tks a lot

elkniwt:

Hi Superbugs,

I do it this way :
$70 - $52 = $18
$54 - $52 = $2
$18 / $2 = 9
Total = 9

This is how I explain to my dd and she could grasp:
The extra lamp is $18 more than the average. The extra is distributed to the rest of the lamps ($2 to each lamp) to raise the average to $54. So total 9 lamps including the new one.

Superbugs:

Nanyang SA2 Q29:
Lili bought some table lamps and the average cost of the lamps was $52. When she bought another table lamp which cost $70, the average cost then became $54. What was the total number of table lamps she had in the end?

I am able to use algebra to solve but not sure how to explain to my DD. Any simpler method?

My solution is: Let the no. of table lamp be X.
$70 + $52X = $54 (X-1)
2X= 16
X= 8
Total table lamps = X+1 = 9

[MathIzzzFun]

Superbugs:

Nanyang SA2 Q29:

Lili bought some table lamps and the average cost of the lamps was $52. When she bought another table lamp which cost $70, the average cost then became $54. What was the total number of table lamps she had in the end?

I am able to use algebra to solve but not sure how to explain to my DD. Any simpler method?

My solution is: Let the no. of table lamp be X.
$70 + $52X = $54 (X-1)
2X= 16
X= 8
Total table lamps = X+1 = 9

Hi

model might help..

http://i54.tinypic.com/2whgt54.jpg\">

cheers.

[lemofish]

Superbugs:

Nanyang SA2 P2 Q16

Yili, Lynn and Devi went shopping. Yili spent 0.25 of the total amount Lynn and Devi spent, while Devi spent 4/11 of the total amount Yili and Lynn spent. Lynn spent $37.50 more than Yili. If Lynn had $90 before she went shopping, what fraction of her money did she spend? Express your answer in its simplest form.
Pls help

Yili:Lynn+Devi=1:4=3:12=15 units
Devi:Yili+Lynn=4:11=15 units
Lynn spend = 12units - 4 units=8 units
Yili:Lynn:Devi=3:8:4
Since Lynn spent $37.50 more than Yili,
5 units=$37.50
1 unit= $7.50
Amount of money Lynn spent= 8units*$7.50=$60
Fraction of money Lynn spent= 60/90=2/3

[leelk]

Crazy this is so difficult! Are u sure this is for P2??

[jtparent]

MathIzzzFun:

jtparent:

Hi,


was lost in dealing fractions / %. Pls help on the following qs:

1. At a toy fair 40% of those present were boys . 8/15 of the remainder were girls & the rest were adults. There were 480 more boys than adults. How many more children than adults were there at the toy fair?

TIA

Hi

1. Boys = 40%, Girls + Adults = 60%
Girls = 8/15 x 60% = 32%, Adults = 60% - 32% = 28%

480 more boys than adults, so 40$ - 28% = 12% = 480, 1% = 40

Total children = 100% - 28% = 72%
72% - 28% = 44% = 44 x 40 = 1760

there were 1760 more children than adults.

cheers.

Thanks! You are great!

[jtparent]

MathIzzzFun:

jtparent:

Hi,


was lost in dealing fractions / %. Pls help on the following qs:

2. Last mth, David use $840 of his salary to buy a laptop. He spent 1/8 of the remaining salary on rent, $400 on food & saved the rest. The amount that he spent on food was $20 less than that spent on rent.
a. What was his salary?
b. What % of his salary did he save?


TIA

Hi

2. Amount spent on rent = 1/8 remaining salary = $400 + $20 = $420
So, total remaining salary (after spending $840) = 8 x $ 420 = $ 3360
a. Salary = $840 + $3360 = $ 4200

b. .. I think you can complete this

cheers.

Thanks! Appreciate your prompt reply!

[lizawa]

leelk:

Crazy this is so difficult! Are u sure this is for P2??

Ahem... \"P2\" refers to \"Paper 2\", not primary 2

[jtparent]

MathIzzzFun:

jtparent:

Hi,


was lost in dealing fractions / %. Pls help on the following qs:

3. Larry spent $60 less than 5/8 of his money on a MP3 player & $25 more than 7/9 of his remaining money on assessment books. After buying the assessement books, he still had $10 left.

a. How much money was left after Larry bought the MP3 player but before he bought the assessment books?
b. How much money did Larry have at first?

TIA

Hi

for this question.. work backwards..

After spending 7/9 remaining + $25 --> $10 left
So, $10 + $25 = $35 = 2/9 remaining money.
Money remaining (after spending on MP3) = 35/2 x 9 = $ 157.50

MP3 player = 5/8 of Larry's money - $60
Money remaining (after buying MP3) = 3/8 of Larry's money + $60
3/8 of Larry's money = $157.50 - $60 = $97.50
Larry's money = $ 97.50/3 x 8 = $ 260

cheers.

Hi,

sorry was confused on this wk backwards.

Is there other simpler method

[MathIzzzFun]

jtparent:

MathIzzzFun:

[quote=\"jtparent\"]Hi,


was lost in dealing fractions / %. Pls help on the following qs:

3. Larry spent $60 less than 5/8 of his money on a MP3 player & $25 more than 7/9 of his remaining money on assessment books. After buying the assessement books, he still had $10 left.

a. How much money was left after Larry bought the MP3 player but before he bought the assessment books?
b. How much money did Larry have at first?

TIA

Hi

for this question.. work backwards..

After spending 7/9 remaining + $25 --> $10 left
So, $10 + $25 = $35 = 2/9 remaining money.
Money remaining (after spending on MP3) = 35/2 x 9 = $ 157.50

MP3 player = 5/8 of Larry's money - $60
Money remaining (after buying MP3) = 3/8 of Larry's money + $60
3/8 of Larry's money = $157.50 - $60 = $97.50
Larry's money = $ 97.50/3 x 8 = $ 260

cheers.

Hi,

sorry was confused on this wk backwards.

Is there other simpler method [/quote]Hi

I am afraid you will have to find a method or \"devise\" a method to work backwards - there are quite a few ways ..

Here is one using branching:

http://i51.tinypic.com/23vl4s6.jpg\">

cheers.