Q&A - P5 Math

[tianzhu]

happyheart:

Please help. Thank you.


Q) Both shops , ABC and XYZ , offered a 15% discount for the same type of mattress. If Mr. Muthu were to buy from shop XYZ, he would have paid $38.25 less than the discounted price in Shop ABC.

a) What was the difference in the original price of the mattress between the two shops?

b) The original price of the mattress in Shop ABC was $1510. What was the minimum percentage discount it must offer so that the discounted price in Shop ABC would be lower than the discounted price in shop XYZ? Give your answer correct to the nearest percent.

Hi

15% ------- 38.25

100% ------- 255 (original price in XYZ)

For ABC ------ 255*100/85 ------- 300

a)Difference -------300 – 255 ------- 45

For (b)

Discounted price in ABC -------- 1510*0.85 ------ 1283.50

Discounted price in XYZ -------- 1283.50 – 38.25 ------- 1245.25

1510 – 1425.25 ------- 264.75

264.75/1510*100% ------- 18%

Best wishes

[happyheart]

tianzhu:

happyheart:

Please help. Thank you.


Q) Both shops , ABC and XYZ , offered a 15% discount for the same type of mattress. If Mr. Muthu were to buy from shop XYZ, he would have paid $38.25 less than the discounted price in Shop ABC.

a) What was the difference in the original price of the mattress between the two shops?

b) The original price of the mattress in Shop ABC was $1510. What was the minimum percentage discount it must offer so that the discounted price in Shop ABC would be lower than the discounted price in shop XYZ? Give your answer correct to the nearest percent.

Hi

Just curious, where is your question from?

15% ------- 38.25

100% ------- 255 (original price in XYZ)

For ABC ------ 255*100/85 ------- 300

a) Difference -------300 – 255 ------- 45

Discounted price@15% in XYZ ------- 216.75

So from 1510, there will be an 86% discount.

Best wishes

Hi Tianzhu,
Thank you for your help. Can you explain how can we teach the kid to see that 15%~$38.25? I cannot connect that to start working on the question. The rest of the steps are quite clear.

The question is from DS teacher.

[happyheart]

tianzhu:

happyheart:

one more please.


Q) There were 1600 pupils in a primary school. when the number of boys increased by 76 and the number of girls decreased by 4%, the total enrolment in the school increased by 3%. How many boys were there in the school at first?

Hi

Where is this question from?

It helps to start with a simple diagram.

1.03*1600 ----- 1648

76 – 48 ------ 28

4% of girls ------- 28

100% of girls ------- 700

Number of boys@first ------- 900

Best wishes

Thanks Tianzhu, I see how you use working backwards method.
This question is also from DS teacher.

[tianzhu]

happyheart:

Hi Tianzhu,
Thank you for your help. Can you explain how can we teach the kid to see that 15%~$38.25? I cannot connect that to start working on the question. The rest of the steps are quite clear.

The question is from DS teacher.

Hi

I'll try to put on slide and PM to you.

Please give me some time.

Best wishes

[cimman]

please refer to the solution below:

[cimman]

G

happyheart:

one more please.


Q) There were 1600 pupils in a primary school. when the number of boys increased by 76 and the number of girls decreased by 4%, the total enrolment in the school increased by 3%. How many boys were there in the school at first?

if your child is willing to use algebra, here is an alternative way:
http://i50.tinypic.com/2n1ezih.png\">

[kyy]

Appreciate of someone can help explain how to solve this. Thanks.


Mr Noor paid $1740 for a total of 25 soccer balls and basketballs. Each soccer ball cost $84 and each basketball cost $48. How many of each type of ball did he buy.

[MathIzzzFun]

kyy:

Appreciate of someone can help explain how to solve this. Thanks.


Mr Noor paid $1740 for a total of 25 soccer balls and basketballs. Each soccer ball cost $84 and each basketball cost $48. How many of each type of ball did he buy.

variation of the \"chicken & cows\" question

$1740--> think total number of legs
25 soccer balls & basketballs --> think total number of animals
1 soccer ball cost $84 --> think 1 cow has 4 legs
1 basketball cost $48--> think 1 chicken has 2 legs
can u work it out?

cheers.

[kyy]

MathIzzzFun:

kyy:

Appreciate of someone can help explain how to solve this. Thanks.


Mr Noor paid $1740 for a total of 25 soccer balls and basketballs. Each soccer ball cost $84 and each basketball cost $48. How many of each type of ball did he buy.

variation of the \"chicken & cows\" question

$1740--> think total number of legs
25 soccer balls & basketballs --> think total number of animals
1 soccer ball cost $84 --> think 1 cow has 4 legs
1 basketball cost $48--> think 1 chicken has 2 legs
can u work it out?

cheers.

Managed to figure out. Thanks!

[zeemimi]

tianzhu:

zeemimi:

Pls help. Thank u.


The avg # of sit ups performed by 15 girls and some boys was 50.
The avg # of sit UPS performed by the girls was 80% of the avg # of situps performed by all the pupils.
The avg # of situps performed by the boys was 30% more than the avg # of situps performed by the girls.
A) what was the avg #of situps performed by the girls?
B) what% of the pupils were boys?

avg # of sit ups performed by 15 girls and some boys ------ 50.
avg # of sit UPS performed by the girls -------- 80% of 50 ------- 40
avg # of situps performed by the boys -------- 130% of 40 ------- 52

15*10 -------- 150
52 – 50 -------- 2
Number of boys ------ 150/2 ------- 75

75/90*100% -------- 83.33% (83 1/3)
Best wishes

thank you! problem taken from RGS 2011 SA2.

Could you explain this part?
15*10 -------- 150 (why 10?)
52 – 50 -------- 2
Number of boys ------ 150/2 (why?)