Q&A - PSLE Math

[tianzhu]

Michaelia0816:

Pls help, quite urgent, cannot understand what this question saying,


http://t.co/zaxc2Izu

Hi

If it's 1/5 mark, I'd go for 1/8.

Best wishes

[paranoid]

http://i49.tinypic.com/2njc4ko.jpg\">

Killer question from Nanyang Prelim paper
Could someone help me

Thanks so much.

[MathIzzzFun]

paranoid:

http://i49.tinypic.com/2njc4ko.jpg\">

Killer question from Nanyang Prelim paper
Could someone help me

Thanks so much.

discussed at http://www.kiasuparents.com/kiasu/forum/viewtopic.php?f=69&t=280&start=7950

cheers.

[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

[tianzhu]

Hi


Please refer to MathIzzzFun’s solution.

Best wishes

[Michaelia0816]

Ok!

[match3frog]

Thanks tianzhu, the question is from ds’s school worksheet. I will ask him to check the question again.


Here’s another one:

Mr Siew drove from Town X to Town Y at 60km/h. If he increased his speed by 12km/h, he would reach Town Y 1 hour earlier. Find the speed he must travel after the first 120km so that he can reach Town Y 4/5h earlier.

Thank you.

[paranoid]

MathIzzzFun:

paranoid:

http://i49.tinypic.com/2njc4ko.jpg\">

Killer question from Nanyang Prelim paper
Could someone help me

Thanks so much.

discussed at http://www.kiasuparents.com/kiasu/forum/viewtopic.php?f=69&t=280&start=7950

cheers.

Thanks for your easy-to-understand explanation. It makes the question much easier to solve.

[tianzhu]

match3frog:

Here's another one:

Mr Siew drove from Town X to Town Y at 60km/h. If he increased his speed by 12km/h, he would reach Town Y 1 hour earlier. Find the speed he must travel after the first 120km so that he can reach Town Y 4/5h earlier.

Thank you.

Hi

If your child is familiar with inverse ratio method, here’s the solution.

Speed ratio -------- 60:72 ------- 5:6

Time ratio --------- 6:5

At 60km/h, he took 6h

At 72km/h, he took 5h

Distance between X and Y --------- 360 km

First 120km at 60km/h, remaining 240km.

240/60 ------ 4h

4 – 0.8 ------ 3.2

Speed after first 120km ------- 240/3.2 ------- 75km/h

Best wishes

[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.