Hi PSLEguru, :thankyou: so much for your help.

Hi. Could someone help me out with the following please. Thank u in advance. Image 4 of 4


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Hi. Could someone help me out with the following please. Thank u in advance. Image 3 of 4


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Hi. Could someone help me out with the following please. Thank u in advance. Image 2 of 4


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Hi. Could someone help me out with the following please. Thank u in advance. Image 1 of 4


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tianzhu:

altp10:

[quote=\"altp10\"]

Hi. I think I managed to solve this myself. However would still like to have some advice to confirm my answer.


According to first two sentences, J wins by 10m.
So breaking the 100m into 10 segments of 10m each, J would be faster than C by 1m in every segment. This also mean J runs 11m while C runs 10m.

a) Since J runs 11m (J adds 11) & C runs 10m (C adds 10):
J C
-10 0
1 10
12 20
23 30
34 40
45 50
56 60
67 70
78 80
89 90
100 100
Answer to a) Tie between the 2 boys.

b) Since J runs 11m (J adds 11) & C runs 10m (C adds 10):
J C
0 10
11 20
22 30
33 40
44 50
55 60
66 70
77 80
88 90
99 100
Answer to b) C won.

Please do advise if I'm correct.
Thank you.

(Sorry I can't load any diagrams as I'm typing these using iPhone)

Hi

You may solve this question by listing, but a more efficient way is to make use of speed ratio.

Joel & Cliff ran a 100m race in which Joel crossed the finishing line just as Cliff reached the 90m mark.

This means for every 10m covered by Joel, Cliff ran 9m.

(a)Joel is the winner

Joel is required to cover 110m.He covered 10m at one interval; hence he needed 11 intervals to finish 110m. At 11 intervals, Cliff covered 99m, therefore short of the finishing point of 100m.

(b)They finish at the same time.

Joel needed to run 100m and Cliff was required to run 90m.At an interval of 10m, Joel completed the race (100m) at 10 intervals. At 10 intervals, Cliff completed 90m, hence arriving at the same time as Joel.

Best wishes[/quote]
Hi Tianzhu,

Alright now I get it..
I had taken J=11m & C=10m
It should be J=10m & C=9m instead.

Thanks Tianzhu & PapayaDad.
Regards

PapayaDad:

altp10:

Hi. I need help with the following Speed question.


Joel & Cliff ran a 100m race in which Joel crossed the finishing line just as Cliff reached the 90m mark.
a) Since Joel won the first race by 10m, he decided to start the second race 10m behind the starting line. Both boys ran at the same speed as in the first race. Who won the second race?
b) In the third race, Cliff started 10m ahead of the starting line. Again assuming that both boys ran at the same speed as in the first race, who was the winner of this race?

Thank you in advance.

I assume Joel finish the race in 10 seconds. That means his speed is 10 meters per second. At that time (10 second) Cliff only reach 90m ; so Cliff speed is 9 meters per second.

Joel start 10 meters behind, meaning he need to cover 110 meters, his speend is 10 meters per second, so he took 11 seconds.

Cliff speed is 9 meters per second, at 11 second he is at 99meter only, still behind Joel.

Cliff then start 10m in front, need to cover 90 meters, his speed is 9 meter per second, so complete in 10 seconds. Joel also took 10 second to reach. so they reach together.

Hi PapayaDad,

Thank u for the advise. However, in my solution in Pg 885, I seemed to have derived a different answer.. Could u kindly advise me on my solution please?

Thanks alot.

altp10:

Hi. I need help with the following Speed question.


Joel & Cliff ran a 100m race in which Joel crossed the finishing line just as Cliff reached the 90m mark.
a) Since Joel won the first race by 10m, he decided to start the second race 10m behind the starting line. Both boys ran at the same speed as in the first race. Who won the second race?
b) In the third race, Cliff started 10m ahead of the starting line. Again assuming that both boys ran at the same speed as in the first race, who was the winner of this race?

Thank you in advance.

Hi. I think I managed to solve this myself. However would still like to have some advice to confirm my answer.


According to first two sentences, J wins by 10m.
So breaking the 100m into 10 segments of 10m each, J would be faster than C by 1m in every segment. This also mean J runs 11m while C runs 10m.

a) Since J runs 11m (J adds 11) & C runs 10m (C adds 10):
J C
-10 0
1 10
12 20
23 30
34 40
45 50
56 60
67 70
78 80
89 90
100 100
Answer to a) Tie between the 2 boys.

b) Since J runs 11m (J adds 11) & C runs 10m (C adds 10):
J C
0 10
11 20
22 30
33 40
44 50
55 60
66 70
77 80
88 90
99 100
Answer to b) C won.

Please do advise if I'm correct.
Thank you.

(Sorry I can't load any diagrams as I'm typing these using iPhone)

Hi. I need help with the following Speed question.


Joel & Cliff ran a 100m race in which Joel crossed the finishing line just as Cliff reached the 90m mark.
a) Since Joel won the first race by 10m, he decided to start the second race 10m behind the starting line. Both boys ran at the same speed as in the first race. Who won the second race?
b) In the third race, Cliff started 10m ahead of the starting line. Again assuming that both boys ran at the same speed as in the first race, who was the winner of this race?

Thank you in advance.

tianzhu:

altp10:

Hi Tianzhu,


It's from St. Andrews.. 1st time I encountered this.

How did u derive the 1 part---- 8?
And the 60?

I understand that since the sharing ratio is 5:3:4 it means it would be a multiple of 12. But is a little bit of guess and check involved to attain the 60?

Thank u.

Hi

Yes, you may use GC, but it tends to be less efficient especially at upper primary level.

A neat way to solve this question is to use MD.

Hope this helps.

Best wishes

http://farm9.staticflickr.com/8515/8575849299_dec8bcbc97_z.jpg\">

Hi Tianzhu,

Thanks alot... Very clear explaination..

Regards