Q&A - PSLE Math

[Vanilla Cake]

small:

Hi all,

Thanks for your time. My DD's answer is 5pm.[quote]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?

[/quote]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

[small]

tianzhu:

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, :celebrate:

Can you show me the working? Thanks in advance.


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

[heutistmeintag]

Hi all, need urgent help on these 3 questions. TIA!


http://www.postimage.org/image.php?v=aVpF3Nr

http://www.postimage.org/image.php?v=aVpFqeJ

http://www.postimage.org/image.php?v=Pq1p_BgA

[small]

small:

Hi Tianzhu, :celebrate:


Can you show me the working? Thanks in advance.


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

Hi Tianzhu and Vanilla Cake, I managed to figure out the working, thanks for oyur help. :celebrate:

[tianzhu]

Hi moderator


Please help to delete this post.

Thank you

[tianzhu]

small:

Hi Tianzhu and Vanilla Cake, I managed to figure out the working, thanks for oyur help. :celebrate:

Hi
This is quite an interesting question.Great, you've got it.

Enjoy your journey.

Best Wishes

[Dharma]

http://www.postimage.org/

[Priskhipo]

heutistmeintag:

Hi all, need urgent help on these 3 questions. TIA!


http://www.postimage.org/image.php?v=aVpF3Nr

http://www.postimage.org/image.php?v=aVpFqeJ

http://www.postimage.org/image.php?v=Pq1p_BgA

Hi heutistmeintag,

The solutions are as follow:


http://www.postimage.org/


http://www.postimage.org/



http://www.postimage.org/

[Tang]

Vanilla Cake:

small:

Hi all,

Thanks for your time. My DD's answer is 5pm.[quote]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[/quote]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]

Hi Dharma and Tang,


thanks for your help.

:celebrate: