Q&A - PSLE Math

[sall]

tianzhu:

Michaelia0816:

Also this one, help!


The ratio of the average speed of Ali, Ben and Carl was 2:3:4 respectively. They started driving at the same time and after 5h, they had covered a total of 675 km. What was the average speed of Ben?

Hi

A:B:C --------2:3:4(Speed)
A:B:C --------2:3:4(Distance)

Distance varies in direct proportion to speed.

9 units -------- 675
1 unit ------- 75
Ben -------- 3*75 ------- 225 km

Average speed of Ben ------- 225/5--------- 45 km/h

Best wishes

Thanks. This is my answer too.

[Michaelia0816]

The question stated Roy.

[Michaelia0816]

At 9.50 am, a lorry left Town J for Town K at an average speed of 54km/h. 50 minutes later, a car left Town K for Town J at an average speed equivalent to 150% that of the lorry. By noon, the lorry and the car was 30 km apart.

a) How far apart was Town J from Town K?
b) How far away from Town J did the lorry pass the car?

[Michaelia0816]

Raju started jogging from point G to point H at 1 pm while Abu started to cycle from Point H to point G at 2 pm. Abu was cycling 3 times the speed of Raju who was jogging at 6km/h. The distance between Point G to point H is 54km.

a) how far from G did they passed each other ?
b) At what time did they pass each other?

[small]

Please help with this speed question and many thanks in advance.


Question:
Mr Thomas left for Town B from Town A at 7.30am. He drove at an average speed of 70 km/h.Some time later, Mr Raja drove from Town A to Town B along the same route. He overtook Mt Thomas at 11.30am. 30minutes later, Mr Raja arrived at Town B while Mr Thomas was stil 5km away from Town B.

a) What was Mr Raja's average speed?
b) Find the distance between Town A and Town B.
c) At what time did Mr Raja leave Town A?

[MathIzzzFun]

small:

Please help with this speed question and many thanks in advance.


Question:
Mr Thomas left for Town B from Town A at 7.30am. He drove at an average speed of 70 km/h.Some time later, Mr Raja drove from Town A to Town B along the same route. He overtook Mt Thomas at 11.30am. 30minutes later, Mr Raja arrived at Town B while Mr Thomas was stil 5km away from Town B.

a) What was Mr Raja's average speed?
b) Find the distance between Town A and Town B.
c) At what time did Mr Raja leave Town A?

Hi

at 1130, Raja and Thomas were at the same point.
At 1200, Thomas travelled another 1/2 x 70 = 35 km, Raja travelled 35 + 5 = 40 km in 1/2 h
Raja's speed = 40 x 2 = 80 km/h .. b & c can then be calculated

cheers.

[tianzhu]

Michaelia0816:

At 9.50 am, a lorry left Town J for Town K at an average speed of 54km/h. 50 minutes later, a car left Town K for Town J at an average speed equivalent to 150% that of the lorry. By noon, the lorry and the car was 30 km apart.

a) How far apart was Town J from Town K?
b) How far away from Town J did the lorry pass the car?

Hi

From 9.50 am to 10.40 am, the lorry covered 45km

Car’s speed ------- 81 km/h

From 10.40am to noon --------- 80 mins

Car’s distance -------- 81*4/3 -------- 108
Lorry distance --------5 4*4/3 -------- 72

or combined together
(54+81)84/3 ------- 180

Distance between J and k --------- 180+30+45 --------- 225km

30/155 -------- 2/9h

Lorry covered 2/9*54 ------ 12 km

(b) 45+72+12 ---------- 129km

Best wishes

[tianzhu]

Michaelia0816:

Raju started jogging from point G to point H at 1 pm while Abu started to cycle from Point H to point G at 2 pm. Abu was cycling 3 times the speed of Raju who was jogging at 6km/h. The distance between Point G to point H is 54km.

a) how far from G did they passed each other ?
b) At what time did they pass each other?

Hi girl

From 1pm to 2pm, Raju covered 6km

54 – 6 ------- 48

Raju’s speed ------- 6 km/h
Abu’s speed ------ 18 km/h

48/24 ------- 2h

They met at 4 pm

In 2h, Raju covered 12km

Distance from G -------- 6 + 12 ------- 18 km

Best wishes

[small]

Many thanks again MathIzzzFun…


I realised my mistake, thought they were started from different towns.

[tianzhu]

Michaelia0816:

Help again with the following 3 questions!!!!!!


The diagram shows the road linking town p to town q.
P to q distance is 280km!
Roy passed P at 10am and reached q at 2 pm. Sam drove from p to q at a constant speed of 100km/h and arrived at a at 1.48pm.
a) when did Roy leave p?
b) when Sam reached town q, how far away from town q was Roy?

Hi

I don’t get to see the diagram, but based on your description, I’ll attempt to answer your question.

280/100 ------ 2.8h -------2h 48 minutes

(a)Roy left P at 10 am

Roy’s speed ------ 280/4 -------70km/h

Roy was 12 minutes away

12/60* 70 ------ 14 km

Best wishes