Q&A - PSLE Math

[tianzhu]

jjxy mum:

Hi,

Thank you for your reply, we are still quite confused on the Cynthia's portion.

Hi

Ok, managed to find the pictorial, hope this helps.

Best wishes

http://farm9.staticflickr.com/8155/7674972602_fac8ddb8c5_z.jpg\">

[shell]

Hi


A neat way is to use MD.

Due to time constraints, I’ll work using units.

2/3 of the total value of the twenty-cent coins is the same as 1/2 of the total value of the fifty-cent coins.

Total value of twenty-cent coins ------ 3 units

Total value of fifty-cent coins ------ 4 units

If Beatrice spends 4 fifty-cent coins, the value of the twenty-cent coins and the value of the remaining fifty-cent coins will be the same.

4 fifty-cent coins ------- $2

4 units – 2 ------ 3 units

1unit ------- 2

Total value of twenty-cent coins ------ 3 units ------ $6

Number of twenty-cent coins ------- 30 (600/20).

Another way is to use “SL” and work in a tabulated list.

20 cents: 50cents ------- 3:4 ------- 6:8

8 - 2 ------ 6, hence the condition is satisfied.

Total value of twenty-cent coins ------ 3 units ------ $6

Number of twenty-cent coins ------- 30 (600/20)

Best wishes[/quote]

Thank You!!!! :boogie: :rahrah:

[i_am_not_a_parent]

:lovesite: :thankyou: :udawoman: or :udaman:

Thanks to everyone!!

[zanen]

help ls Two cars race around a circular track at constant speeds starting at the same point. If they travel in opposite directions, then they meet every 30 seconds. If they travel in the same direction, then they meet every two minutes. If the track is 1800m long,what is the speed of each car?

[tianzhu]

zanen:

help ls Two cars race around a circular track at constant speeds starting at the same point. If they travel in opposite directions, then they meet every 30 seconds. If they travel in the same direction, then they meet every two minutes. If the track is 1800m long,what is the speed of each car?

Hi

Could you share with us where you take this question from?

Is this a PSLE type of question?

The answers to your question are 22.5m/s and 37.5m/s.

Best wishes

[enoawng]

tianzhu:

Hi

Could you share with us where you take this question from?

Is this a PSLE type of question?

The answers to your question are 22.5m/s and 37.5m/s.

Best wishes

Correct!

[MathIzzzFun]

zanen:

help ls Two cars race around a circular track at constant speeds starting at the same point. If they travel in opposite directions, then they meet every 30 seconds. If they travel in the same direction, then they meet every two minutes. If the track is 1800m long,what is the speed of each car?

Speed of faster car --> A
SPeed of slower car --> B
If they travel in opposite directions, then they meet every 30 seconds
-->total distance travelled in 30s = 1800m
so, A + B = 1800/30 m/s = 60m/s

If they travel in the same direction, then they meet every two minutes
--> faster car covers 1800m more than slower car in 2 min
ie A-B 1800/120 = 15m/s

A--> (60+15)/2 = 37.5 m/s
B--> 60-37.5 = 22.5 m/s

cheers.

[jjxy mum]

tianzhu:

jjxy mum:

Hi,

Thank you for your reply, we are still quite confused on the Cynthia's portion.

Hi

Ok, managed to find the pictorial, hope this helps.

Best wishes

http://farm9.staticflickr.com/8155/7674972602_fac8ddb8c5_z.jpg\">

Hi,

Thank you very much. Finally, we understand it now.

[Essential]

Hi Tian Zhu thank you for your help for earlier question. One more question from Nanyang Prelim 2012. Q13. 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 discounted price in the shop ABC ?

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 connect to the nearest percent.Thankyou in adv

[david59]

MathIzzzFun:

match3frog:

Please help with the following question:


A car was travelling from Town P to Town Q.

After completing 2/7 of the journey in 1/2 hour, the car passed a van travelling at a constant speed of 70km/h in the same direction.
3 hours later, the car reached Town Q but the van was still 65 km away from Town Q.

(a) Find the average speed of the car.

(b) If the van left Town P at 0810, at what time would it arrive at Town Q?

Thank you

5/7of distance PQ --> 3 x 70 + 65 = 275 km
distance PQ --> 275/5 x 7 --> 385 km
total time taken by car --> 3. 5 h
average speed of car --> 385/3. 5 --> 110 km/h

cheers.

Hi all,
I am inclined to say that the qn is flawed.
If the car's speed is 110km/hr, then in three hours after passing the van and reaching town Q, he would have travelled 330km. However, you rightly calculated that the distance between the point where the car passed the van and town Q is 275km. So, there is a discrepency here.
I suspect the fraction used in the qn is unneccessary. It should have just been \" After travelling for 1/2 hour, the car passed a van travelling at a constant speed of 70km/h in the same direction.
3 hours later, the car reached Town Q but the van was still 65 km away from Town Q\".