Q&A - P5 Math

[PiggyLalala]

pixiedust:

Ah, yes! I managed to get the correct answer, thanks piggylalala!

You're welcome
All the best for the PSLE next year.

[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?

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?

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

[Superbugs]

Need help on this question!

There are 60% as many blueberry muffins as banana muffins and 20% more chocolate muffins than the blueberry muffins. What is the ratio of the number of banana muffins to the number of chocolate muffins?

[MathIzzzFun]

Superbugs:

Need help on this question!

There are 60% as many blueberry muffins as banana muffins and 20% more chocolate muffins than the blueberry muffins. What is the ratio of the number of banana muffins to the number of chocolate muffins?

Hi
Blueberry : Banana = 60 : 100 = 3:5 -- (1)
Blueberry : Chocolate = 100 : 120 = 5:6 -- (2)

(1)x5, (2) x 3
Blueberry : Banana: Chocolate = 15 : 25 : 18

cheers.

[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.

[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.

[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.

[Superbugs]

The figure below is not drawn to scale. The figure is made up triangles drawn within a rectangle. BY and CX are straight lines. The area if rectangle ABCD is 480cm2 and the area of triangle BXZ is 56cm2. Find the total area of the shaded parts.


Sorry that I do not know how to incorporate the diagram herein! Pls help. Tks

[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

[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