## Q&A - PSLE Math

Academic support for Primary 6 and PSLE
small
BlueBelt
Posts: 419
Joined: Wed Dec 17,
tianzhu wrote:Hi

I think the answer is 9am.

Time taken by Mr Ong --> 12 hours
Time taken by Mr Lee --> 15 hrs

Where is this Q from?It can be considered as a higher order speed Q where proportion method may be more appropriate.

Best Wishes
Hi Tianzhu,

Can you show me the working? Thanks in advance.

I am still trying to figure out Vanilla's working....

heutistmeintag
BlueBelt
Posts: 385
Joined: Wed Jun 25,
Hi all, need urgent help on these 3 questions. TIA!

small
BlueBelt
Posts: 419
Joined: Wed Dec 17,
small wrote:Hi Tianzhu,

Can you show me the working? Thanks in advance.

I am still trying to figure out Vanilla's working....
Hi Tianzhu and Vanilla Cake, I managed to figure out the working, thanks for oyur help.

tianzhu
Councillor
Posts: 3787
Joined: Fri May 30,
Total Likes:8
Hi moderator

Thank you
Last edited by tianzhu on Wed Sep 02, 2009 2:31 pm, edited 2 times in total.

tianzhu
Councillor
Posts: 3787
Joined: Fri May 30,
Total Likes:8
small wrote: Hi Tianzhu and Vanilla Cake, I managed to figure out the working, thanks for oyur help.
Hi
This is quite an interesting question.Great, you've got it.

Best Wishes

Dharma
BlackBelt
Posts: 954
Joined: Mon Apr 06,

Priskhipo
YellowBelt
Posts: 21
Joined: Sat Sep 13,
heutistmeintag wrote:Hi all, need urgent help on these 3 questions. TIA!

Hi heutistmeintag,

The solutions are as follow:

Tang
BlueBelt
Posts: 297
Joined: Sat Jun 13,
Vanilla Cake wrote:
small wrote:Hi all,
Question:
Mr Lee left Town M for Town N at a speed of 80km/h. Mr Ong also left Town M for town N one hour later at a speed of 100km/h. Mr Ong reached Town Q, which was was in the middle of Town M and N, 30 mins earlier than Mr Lee. If Mr Ong reached Town N at 10pm, what time did Mr Lee leave Town M?
Hi small,
Is this qn from your DD's P6 Prelim exam? The answer is 9 am.

Difference in distance between Mr Lee and Mr Ong = 1.5 x 80 = 120 km.
Required time for Mr Ong to catch up with Mr Lee = 120 / (100-80) = 6 h
Distance from Town M to Town Q = 6 x 100 = 600 km
Total distance between Town M and Town N = 600 x 2 = 1200 km
Time taken for Mr Ong to travel from Town M to Town N=1200/100 = 12 h

Since Mr Lee started 1 hour earlier, that meant he took 13 h to travel.
Use timeline:

9 am.............12 pm...................10 pm
......................3 h......................10 h
Unlined statement may not be quite correct as Time difference of 1.5 h is not Required time for Mr Ong to catch up with Mr Lee.

Speed of Mr Lee (SL) : Speed of Mr Ong (SO) = 80 : 100 = 4 : 5

For the same distance, SL : SO = TO : TL = 4 : 5

Difference in time, 1 u = 2 x (1 + 0.5) = 3 h

TO : 4 u = 4 x 3 = 12 h

Timeline

9am ..... 1 h ..........10 am..... 2 h ..........12 noon..... 10 h ....... 10 pm
Starting time of Mr Lee = 9 a.m.

small
BlueBelt
Posts: 419
Joined: Wed Dec 17,
Hi Dharma and Tang,