Q&A - PSLE Math

[tianzhu]

Suz855:

Mr Sum had 120 ovens. He sold 40% of the oven at their usual price and half of the remainder at a discount of 15% of the usual price. He sold the rest of the ovens at their cost price of $380 each. He earned $1878. What was the price of each oven after the discount?

Hi Suz855

Good Morning

You may use Number*Value method to solve this question. A diagram may help one to see the problem better.

I believe this is a paper 2 question and you're allowed to use the calculator.

First, work out the number of ovens as follows,

Usual price (UP) ----- 48
85% of UP ----- 36
Cost price ($380) ----- 36

Cost price of 120 ovens ----- (120*380) ----- 45600
He earned $1878, meaning the selling price of 120 ovens is $47478

To avoid working with decimals, I’d use 100u to represent the UP and 85u to show the discounted price.

Therefore the selling prices are as follows

48*100u ----- 4800u
36*85u ----- 3060u
36*380 ----- 13680

They add up to $47478, you’ll get 1u equals to 4.3

3060*4.3/36 ----- 365.50

The discounted price of oven ----- $365.50

Best wishes

[tianzhu]

Brenda10:

Good morning Tianzhu

Yes. You're right that now dd can understand why is 8 units and I believe if there are similar questions in other papers she should be able to handle.

Thank you.

Hi Brenda10

You're welcome.

Best wishes

[Suz855]

Hi Tianzhu,


Yes calculator can be used & thanks for the clear & great solution ....have a great wk ahead

cheers

[Tang]

Suz855:

Hi,


Looking for better way to solve the following question, your kind input will be most appreciated.

Question
Mr Sum had 120 ovens. He sold 40% of the oven at their usual price and half of the remainder at a discount of 15% of the usual price. He sold the rest of the ovens at their cost price of $380 each. He earned $1878. What was the price of each oven after the discount?

Thanks a million
:idea:

100% --> 120 ovens

10% --> 10/100 x 120 = 12

40% --> 4 x 12 = 48 ovens

1/2 x 60% = 30% --> 3 x 12 = 36 ovens

48 + 36 = 84

48 x 1 u + 36 x 0.85 u --> 1878 + 84 x 380 = 33798

1 u --> 33798/78.6 = 430

0.85 u --> 0.85 x 430 = $365.50

The price of oven after discount was $365.50.

[tianzhu]

Suz855:

Hi Tianzhu,


Yes calculator can be used & thanks for the clear & great solution ....have a great wk ahead

cheers

Hi

You're welcome.

Best wishes

[tianzhu]

Brenda10:

DD working

A : P
4 : 7 (End) } 8 : 14
+17 -17 (Changes) } +17 -17
? : ? (Before) } ? : ?

A : P
1 : 1 (End) } 11 : 11
+5 -5 (Changes) } + 5 : -5
? : ? (Before) } ? : ?

11 - 8 = 3
17 - 5 = 12
12 / 3 = 4

Therefore 8 x 4 + 17 = 49

Thank you.

Hi Brenda10

Your ah girl has the right answer.

She has used the Units Method.
She has also demonstrated good understanding to see that the total number of marbles remains the same in both cases.

In doing this question, it’s very important to understand whether to add or subtract the numbers, for example 17-5 or 17+5.

Another alternative is to use MD to solve such question.

Best wishes

[Vanilla Cake]

TIA for your time and effort to provide your answer for this question from Nan Chiau Pri 2010 P6 SA1 Paper 1 Q12 [2 marks]:


Express 2.2% as a fraction.
(1) 2⅕
(2) 2½
(3) 11/50
(4) 11/500

Answer given is option (1) but my P5 younger sister’s answer is option (4).
Which is correct and pls help to explain your selection of option (1) if this option is correct.

A check with Maths textbook - My Pals are Here! - Maths - 2nd edition - 6A published by Marshall Cavendish Education on a worked example on page 141 has the following:

As a fraction: 34/100
As a decimal: 0.34
As a percentage: 34%

[Brenda10]

Vanilla Cake:

TIA for your time and effort to provide your answer for this question from Nan Chiau Pri 2010 P6 SA1 Paper 1 Q12 [2 marks]:


Express 2.2% as a fraction.
(1) 2⅕
(2) 2½
(3) 11/50
(4) 11/500

Answer given is option (1) but my P5 younger sister's answer is option (4).
Which is correct and pls help to explain your selection of option (1) if this option is correct.

A check with Maths textbook - My Pals are Here! - Maths - 2nd edition - 6A published by Marshall Cavendish Education on a worked example on page 141 has the following:

As a fraction: 34/100
As a decimal: 0.34
As a percentage: 34%

Dear VC


DD also given the answer of 11/500

Thank

[tianzhu]

Hi VC


Your sister’s answer is correct.

Best wishes

[Brenda10]

tianzhu:

Hi Brenda10


Your ah girl has the right answer.

She has used the Units Method.
She has also demonstrated good understanding to see that the total number of marbles remains the same in both cases.

In doing this question, it’s very important to understand whether to add or subtract the numbers, for example 17-5 or 17+5.

Another alternative is to use MD to solve such question.

Best wishes

Hi Tianzhu

Thank you.

Now dd is focus on learning the new topics of speed. Hopefully she is able to grasp some basis concept when attempt to speed question.