Q&A - PSLE Math

[kuts]

Thank you green belt for ur wonderful explanation! Tks a lot

[tianzhu]

Michaelia0816:

You meant Unit and Part Method (UP), I tried to find the ways to solve using it, I also think UP is the best way, but sometime, I do forget how to use it!!!

Hi

Good Morning, girl.

Well, forgetting is a natural process.

Sometimes, adults forget too.

It’s comforting to know forgetting and tendency to make careless mistakes are some things all students in the world are capable of making.

The students who make fewer mistakes and lose fewer points than other fellow students will usually fare better.

Well, talking about UP, children at your age are ……..

Usually with their iPad

Usually like to be at the Playgrounds.

Usually PSLE is a Usual Part of a child’s life.

It’s not the only part; it’s the beginning of a long life journey.

Put in your best efforts, be the best you can be.

Pay attention to your teachers and listen to your Understanding Parents.

Learn UP, understand UP and apply UP and your marks will go UP. If you want to forget UP, please do it after PSLE.

Here’s another slide which I hope will help to reinforce your understanding of UP.As you can see, the concept is not too difficult to grasp. The steps are rather mechanical and not too tedious. Equalise the final parts and you’re on the way to your 5 points.

Enjoy your studies.

Best wishes

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[lousymum]

Help pls.


(1) Michael jogged while Karen walked from the same place but in opposite directions along a straight road. After 5h, they were 30 km apart. Michael’s average speed was 1.2 km/h faster than Karen’s average speed. What was Karen’s average walking speed?

(2) Ben and Macus received some moey from their mother. Marcus would have $64 more than Ben if Ben gave 2/5 of his share to Marcus. Marcus would have $144 more than Ben if Ben gave 2/3 of his share to Marcus. How much money did Ben receive from his mother?

Thanks.

[tianzhu]

lousymum:

Help pls.

(1) Michael jogged while Karen walked from the same place but in opposite directions along a straight road. After 5h, they were 30 km apart. Michael's average speed was 1.2 km/h faster than Karen's average speed. What was Karen's average walking speed?

Hi

There’s a few ways to solve it.

For questions on Speed, it’s useful to start with a simple diagram.

If Karen’s distance travelled in 5h is showed by 1 unit or 1 box, then Michael’s distance travelled in 5h would be 1 unit or 1 box + (5*1.2)

Hence we have 2 boxes or units + 6 ------- 30

This gives 1 unit/box ------- 12

Therefore, Karen’s speed -------- 12/5 ------- 2.4

Best wishes

[tianzhu]

lousymum:

(2) Ben and Macus received some moey from their mother. Marcus would have $64 more than Ben if Ben gave 2/5 of his share to Marcus. Marcus would have $144 more than Ben if Ben gave 2/3 of his share to Marcus. How much money did Ben receive from his mother?

Hi

There are two scenarios in this question.

Marcus would have $64 more than Ben if Ben gave 2/5 of his share to Marcus.

A common multiple of 3 and 5 is 15

Marcus -------9 units + 64
Ben -------- 9 units

Marcus would have $144 more than Ben if Ben gave 2/3 of his share to Marcus

Marcus -------5 units + 144
Ben -------- 5 units

The total amount of money in both scenarios stays the same.

18 units + 64 ------- 10 units + 144
8 units -------- 80
1 unit ------- 10

Ben ------- 15 units -------- 150

Best wishes

[lousymum]

Hi tianzhu,


hmm... yr answers are so much easiler to digest, :thankyou:

[koguma]

tianzhu:

lousymum:

Help pls.

(1) Michael jogged while Karen walked from the same place but in opposite directions along a straight road. After 5h, they were 30 km apart. Michael's average speed was 1.2 km/h faster than Karen's average speed. What was Karen's average walking speed?

Hi

There’s a few ways to solve it.

For questions on Speed, it’s useful to start with a simple diagram.

If Karen’s distance travelled in 5h is showed by 1 unit or 1 box, then Michael’s distance travelled in 5h would be 1 unit or 1 box + (5*1.2)

Hence we have 2 boxes or units + 6 ------- 30

This gives 1 unit/box ------- 12

Therefore, Karen’s speed -------- 12/5 ------- 2.4

Best wishes

Hi Tianzhu, I tried to following your steps for the following qns but I get stuck. Appreciate if you can advise on this qns. Thanks.

A cargo train leaves city X for city Y, 1500km apart at 8am. At the same time, express train leaves city Y for city X. Express train travels at a speed 100km/h faster than cargo train.
The 2 trains pass each other and they are 300km apart at 8pm. What is the speed of express train?

[tianzhu]

Hi koguma


Please refer to MathIzzzFun’s solution.

Best wishes

[MathIzzzFun]

koguma:

A cargo train leaves city X for city Y, 1500km apart at 8am. At the same time, express train leaves city Y for city X. Express train travels at a speed 100km/h faster than cargo train.
The 2 trains pass each other and they are 300km apart at 8pm. What is the speed of express train?

Hi

Draw a diagram for the journey..
1st part of the journey -- cargo train and express train meet --> total distance travelled (by both) = 1500 km
2nd part of journey -- cargo train and express train \"separate\" and go opposite way --> additional distance covered = 300 km in total.
Total distance covered in 1st part & 2nd part of journey --> 1800 km --(A)

Since express train travels 100 km/h faster, after 12 hours (8am to 8pm), the express train will cover 100 km x 12 h = 1200 km more than the cargo train.

So, distance covered by express train --> (1800 + 1200) / 2 = 1500 km
Express train's speed --> 125 km/h
Cargo train's speed --> 25 km/h

or ..from (A) and total time from 8am - 8pm = 12h,
total speed (cargo + express) = 1800 km/ 12h = 150 km/h
since express train's speed is 100 km/h more than cargo train,
express train's speed --> (150 + 100) /2 = 125 km/h

cheers.

[Chan09]

Why would you divide by 2?

distance covered by express train –> (1800 + 1200) / 2 = 1500 km