Q&A - PSLE Math

[Michaelia0816]

tianzhu:

Michaelia0816:

6) A van left Town X for Town Y at 8am. After travelling for 5hr at its usual speed,the van stopped for 30 min for lunch break. In order to reach Town Y at 4 pm, the speed of the van was increased by 16km/h.Find the distance between Town X and Town Y?

Hi

5h from 8am ------ 1pm
1pm ------- 4pm -------- 3h

But he increased speed by 16km/h to catch up with ½ h lunch.

In 2.5 h he covered (2.5*16) or 40 km more.

Usually the van took 1/2h to travel 40 km

Therefore its speed ------ 40*2 ------ 80 km/h

8am to 4pm ------8 h

Distance between X and Y -------- 50*8 ------ 640 km

Best wishes

Maybe is your typepo error, it should be 80.

[Michaelia0816]

tianzhu:

Michaelia0816:

Thank again, I had to admit I didn't think of that method to comple yeh.

Hi

You're welcome.

You are a smart young lady.You'll get better.

Best wishes

Thank for your praise!!!!

[Michaelia0816]

Left 5 more question to solve, pls help with method!! K?

[Michaelia0816]

Wish Tianzhu will help to solve the other 5 questions!

[tianzhu]

Michaelia0816:

Maybe is your typepo error, it should be 80.

Hi

It should be read as 80.

I'll revise the solution.

Best wishes

[tianzhu]

Michaelia0816:

Next 3 question.....

5) A cab driver drove from Town A To Town B. He passed a lorry driver who was driving at 100km/h in the opposite direction from Town B to Town A. One and a half hour after they passed each other, the cab driver arrived at Town B but the lorry driver was still 60km away from Town A.
A) Assuming that both drivers passed each other at mid-way between Town A and B, what is the total distance between the two towns?
B) If the lorry driver arrived in Town B at 1800, what time did he start to drive from Town A?

Hi

Again, start with a simple diagram.

In 1.5h, the lorry covered 1.5*100 or 150 km.

150+60 ----- 210 km

Distance between A and B ------ 210*2 -------- 420 km.

Time taken by lorry driver ------ 420/100 ------ 4.2 h ------- 4h 12min

Work backwards from 1800h, he started at 1348 h

Best wishes

[tianzhu]

Michaelia0816:

4) A car and a coach travelled from Town A to Town B. The coach left Town A at 0648 and it took 5 hr to reach Town B. The car started 30 min later than the coach and it took 4 hr to reach Town B. At what time did the car catch up the coach?

Hi girl

I thought you've a tutor, how come you didn't ask your tutor for help.

There are a few ways to solve this questions.If you're familiar with inverse ratios or proportion, you may also use it.

LCM of 4 and 5 is 20.
Distance between the 2 towns is 20 units

Coach
5 hours for 20 units
1 hour for 4 units

Car
4 hours for 20 units
1 hour for 5 units

Coach’s head start = 1/2x4units = 2 units

Hence, the car needed to catch up with these 2 units due to its late start.

Car caught up by a unit in 1 hour

2 units will need 2 hours; this means the car needs 2 hours to catch up with the coach.

From 0648h add a duration of (1/2h + 2h) ------- 0918h

The car caught up with the coach at 0918

Best wishes

[tianzhu]

Michaelia0816:

Next 2 questions...

3) Mr Kang wanted to travel from Town A to B. At first, he travelled at an average speed of 70 km/h. After travelling 84 km, ge increased his speed by 14 km/h to complete the remaining 1/3 of his journey.
A) What was the distance between Town A and Town B?
B) How much time could he saved if he travelled at a constant speed of 90km/h for the entire trip?

Hi

Start with a simple diagram.

2 units ----- 84 km
3 units ------ 126 km (distance between Town A and Town B)

126/90 ------ 1.4h
84/70 ------ 1.2h
42/84 ------ 0.5h

Time saved ------ 1.7 – 1.4 ------ 0.3h or 18 minutes.

Best wishes

[Michaelia0816]

Oh, the tutor was oversea so cannot

[tianzhu]

Michaelia0816:

2) Mr Tan was travelling from Sandy Town to Lawang Town. A truck travelling at a uniform speed of 60 km/h headed the same way.After completing 4/9 of the journey, Mr Tan passed the truck. 4 hour later, Mr Tan arrived at Lawang Town while the truck was still 10 km away from it.
A) How far was Lawang Town from Sandy Town?
B) At what time did Mr Tan leave Sandy Town if he reached Lawang Town at
3 pm

Hi

Start with a simple diagram.

In 4h, the truck covered 4*60 or 240 km.

240 + 10 ----- 250
5 units ------ 250
1 unit ------ 50

9 units ------ 450 (Distance between Lawang Town from Sandy Town)

Mr Tan’s speed ------- 250/4 ------ 62.5 km/h

Time taken by Mr Tan ------ 450/62.5 ------ 7.2h -------7h 12 minutes

Hence, he started at 0748h

Please check your Q1(Mr Lee), where is it from?

Best wishes