P6 Speed Question, Please help!
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A train travels at 30 km/h and a car travels at a certain uniform speed. The train left Town A 3 hours before the car, but the car overtook the train 6 hours after it had set off and arrived at Town B 2 hours before tha train.
(a) What is the speed of the car?
(b) What is the distance bewteen the two towns?
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The car overtake the train in 6 hrs. Train has already travelled 9 hrs before being overtaken.
Dist train travel = 9 X 30 = 270
Spd of car = 270 / 6 = 45km/hr
Let dist between the towns be x
x/30 = x/45 + 5
Solving that gives x = 450km
If you don't know how to use algrebra, draw the model out which i am lazy to do.
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Originally posted by dkcx:
The car overtake the train in 6 hrs. Train has already travelled 9 hrs before being overtaken.
Dist train travel = 9 X 30 = 270
Spd of car = 270 / 6 = 45km/hr
Let dist between the towns be x
x/30 = x/45 + 5
Solving that gives x = 450km
If you don't know how to use algrebra, draw the model out which i am lazy to do.
Friend, p6 cannot use algebra la
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Originally posted by Uncertain:
Friend, p6 cannot use algebra la
Then draw the model for him then, i'm lazy to do so. As least the answers have been given to him and we do have P6 who knows algebra and uses it.
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still thinks it's very silly that P6 can't use algebra when it's much easier and you'll be using it all the way to uni =P if taking math at uni level of course.
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Originally posted by ThunderFbolt:
still thinks it's very silly that P6 can't use algebra when it's much easier and you'll be using it all the way to uni =P if taking math at uni level of course.
What MOE is worried about is letting students using algebra without truly understanding it. They do not want students to just put symbols and numbers together just to get an answer without realising what those symbols stand for. It may sounds silly, but some Pri school students do know how to use algebra, yet are unable to fathom what it all mean, or are able to explain only half of it.
Look on the bright side, USA's grade schools have adopted our model drawing methods and praised it for its "building-up" structure, as students can learn to use more and more advance structures starting from the basics, yet not trailing away from it.
Speed of car = 45km/h, speed of train = 30km/h
Distance which car gains on train per hour = 45km - 30km = 15km
Distance which train travels in 2 hours = 30km/h X 2h = 60km
Amount of time which car continued travelling after it reaches the train
= 60km / 15km = 4h
Amount of distance which car continued travelling after it reaches the train
= 45km/h X 4h = 180km
Distance between 2 towns = 270km + 180km = 450km
In the end I am also unable to provide a model diagram.
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Hi forbiddensinner,
For PSLE speed question, students are advised to use/draw the distance/time line.
The bar model drawing method is rarely used in PSLE speed question.
Your method of solving the question is already the typical way to solve the PSLE
Speed question, except that you have not put the question information on a
time/distance line first.
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A train travels at 30 km/h and a car travels at a certain uniform speed. The train left Town A 3 hours before the car, but the car overtook the train 6 hours after it had set off and arrived at Town B 2 hours before the train.
(a) What is the speed of the car?
(b) What is the distance between the two towns?
A.
Because the train left Town A 3 hours early at a speed of 30km/ h, we calculate the advantage the train had over the car.
3 Hours X 30km = 90km advantage
After 6 hour, of driving in the car, the car finally catch up with the train. So now let see how fast does the car catches up per hour.
Take advantage over the time taken
90km / 6 hours = 15 km/ h
Car travel 15km / h faster than train. To get the speed of the car
15km/ h + 30km/ h = 45 km/h
B.
Speed of the car at 45 km/h.
Speed of the train at 30 km /h.
Car reaches Town B 2 hours earlier than train.
Train slower by 60km
Each hour, car faster by train by 15km /h so I take
60 / 15 = 4 hours
So 4 hours is the unknown after the car overtook the train to arrived at Town B.
To find the distance we take
6 hours (mentioned) + 4 hours = 10 hours
10 X 45 km/h = 450 km
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sry, font a bit too big...
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Hello friend, draw model diagram out, this is not long essay question and answer. Your answer got more words than the question leh.
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Originally posted by ditzy:
Hello friend, draw model diagram out, this is not long essay question and answer. Your answer got more words than the question leh.
kk...
