P6 Speed Question, Please help!

kkhing SG

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?

dkcx SG

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.

Uncertain SG

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

dkcx SG

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.

ThunderFbolt SG

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.

Forbiddensinner SG

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.

Lee012lee SG

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.

---Max--- SG

(a) What is the speed of the car?

(b) What is the distance between the two towns?

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

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

---Max--- SG

sry, font a bit too big...

ditzy SG

Hello friend, draw model diagram out, this is not long essay question and answer. Your answer got more words than the question leh.

---Max--- SG

Hello friend, draw model diagram out, this is not long essay question and answer. Your answer got more words than the question leh.

kk...