Ask Singapore Homework?
Upload a photo of a Singapore homework and someone will email you the solution for free.
Question
primary 6 | Maths
| Speed
2 Answers Below
Anyone can contribute an answer, even non-tutors.
Please help to solve and explain. Thank you
Date Posted: 4 years ago
Views: 300
See 2 Answers
done
{{ upvoteCount }} Upvotes
clear
{{ downvoteCount * -1 }} Downvotes
Explanation is inside the picture, hope this helps !
Date Posted:
4 years ago
Yes.Thank you very much for your easy to understand solution.
Thanks
The solution is erroneous. Tom is not always 15km ahead of Ham.
Tom will only be 15km ahead of Ham if they both changed to the same speed after the point Ham reached the ⅓ mark.
Example :
Let's say the distance of the race is 270km.
They do not change their speeds throughout the journey.
Ham travels at 90km/h.
In 1 hour he travels 90km, which is ⅓ of 270km.
Let's assume Tony travels 15km/h faster.
90km/h + 15km/h = 105km/h
Tony travels at 105km/h. In 1 hour, he travels 105km, which is 15km more than Ham.
Now in 2 hours, Ham has travelled 90km x 2 = 180km
Tony has travelled 105km x 2 = 210km in 2 hours.
210km - 180km = 30km
Tony is now 30km ahead of Ham. The distance between them actually increased. It doesn't remain constant at 15km.
Tom will only be 15km ahead of Ham if they both changed to the same speed after the point Ham reached the ⅓ mark.
Example :
Let's say the distance of the race is 270km.
They do not change their speeds throughout the journey.
Ham travels at 90km/h.
In 1 hour he travels 90km, which is ⅓ of 270km.
Let's assume Tony travels 15km/h faster.
90km/h + 15km/h = 105km/h
Tony travels at 105km/h. In 1 hour, he travels 105km, which is 15km more than Ham.
Now in 2 hours, Ham has travelled 90km x 2 = 180km
Tony has travelled 105km x 2 = 210km in 2 hours.
210km - 180km = 30km
Tony is now 30km ahead of Ham. The distance between them actually increased. It doesn't remain constant at 15km.
I've just posted the correct solution. Feel free to check it out and clarify any doubts if any.
This question has actually appeared before. There is an error. It should be that Tony's speed is 90km/h.
This question has actually appeared before. There is an error. It should be that Tony's speed is 90km/h.
Thank you J for your correct solution.It was a useful concept that you explained.
Welcome
When Ham travelled ⅓ of the race, Tony was 15km ahead of him.
15km ÷ 90km/h = 1/6 h = 10min
Tony took 10 min to travel this 15km from the ⅓ mark. This tells you that he actually reached the mark 10 min before Ham.
What this means is for every ⅓ of the race Ham is 10min slower than Tony. He will take 10 min more to finish for every ⅓ of the race.
So for the next ⅓, he would be another 10min slower than Tony than he already was at ⅓ of the race. And for the last ⅓, Ham will yet again be another 10min slower than he already was at ⅔ of the race.
So for the whole race, Ham would be 3 x 10min = 30min slower than Tony
Time Ham reached would be 0935 + 0035 = 1005, which is 10.05am
15km ÷ 90km/h = 1/6 h = 10min
Tony took 10 min to travel this 15km from the ⅓ mark. This tells you that he actually reached the mark 10 min before Ham.
What this means is for every ⅓ of the race Ham is 10min slower than Tony. He will take 10 min more to finish for every ⅓ of the race.
So for the next ⅓, he would be another 10min slower than Tony than he already was at ⅓ of the race. And for the last ⅓, Ham will yet again be another 10min slower than he already was at ⅔ of the race.
So for the whole race, Ham would be 3 x 10min = 30min slower than Tony
Time Ham reached would be 0935 + 0035 = 1005, which is 10.05am
Thanks
360 Tutoring Program