Q&A - PSLE Math

[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

[MathIzzzFun]

Chan09:

Why would you divide by 2?

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

Hi

Draw a simple model,
Bigger block--> expres train
Smaller block --> cargo train
Sum = 1800
Difference = 1200

cheers.

[Neat]

Hi


Tap A can fill a tank completely in 6 minutes. Tap B can fill the same tank completely in 3 minutes. At the beginning, Tap A was turned on to fill the tank. After 1 minute, Tap B was then turned on to fill the tank. How long would it take to fill the tank completely?

Thanks for the time.

[Edureach]

Neat:

Hi


Tap A can fill a tank completely in 6 minutes. Tap B can fill the same tank completely in 3 minutes. At the beginning, Tap A was turned on to fill the tank. After 1 minute, Tap B was then turned on to fill the tank. How long would it take to fill the tank completely?

Thanks for the time.

Let the volume of the tank be in 6 units.

Speed of tap A to fill 1 unit = 1min/6mins for 6 units.
Speed of tap B to fill 1 unit = 30 secs/3mins for 6 units.

Tap A was turned on during 1st min = 1 unit filled.
Tap A & B were turned on during next min = 1+2 units filled.
Time taken to filled 4 units = 2 mins Ans(A).
Balance 2 units to be filled by tap A and B.

It took 60 secs to fill 3 units.
For 2 units time taken = 60 x 2/3 = 40 secs Ans (B).

Total time taken to fill completely = Ans A +B = 2 mins 40 secs.

[superksmum]

Hi, help needed for these questions from Catholic High SA 2011


Ques 16) Jerry bought four times as many pencils as notebooks and spent a total of $21.60. He spent $2.40 more on the notebooks than the pencils. Given that a notebook costs $3.20 more than a pencil, find the cost of a pencil.

Ques 18) at first, Ravi had $200 more than Vincent. He gave 40% of his money to Vincent. Vincent then gave 25% of his money to Ravi. In the end, Vincent had $68 more than Ravi. How much did Vincent give Ravi?


Thank you.

[superksmum]

ACS SA Paper 2011.


Ques 14) Mrs Lee has 60 pencils to give to her class. If she gives each boy 2 pencils and each girl 3 pencils, she will have 6 pencils left over. However, if she gives each boy 3 pencils and each girls 2 pencils, she will have 4 pencils left over. How many pupils are there in Mrs Lee’s class?

Ques: 17) Daphne had 20% fewer books than Jocelyn. Yan Ming had 8 more books than Jocelyn. If Jocelyn were to give 4 books to Daphne, they would both have an equal number of books.

b) Yan Ming went to buy some new books. The ratio of books that Yan Ming had to the ratio that Jocelyn had then become 3:2. How many new books did Yan Ming buy?

Thank you.

[speedmaths.012624com]

superksmum:

Hi, help needed for these questions from Catholic High SA 2011


Ques 18) at first, Ravi had $200 more than Vincent. He gave 40% of his money to Vincent. Vincent then gave 25% of his money to Ravi. In the end, Vincent had $68 more than Ravi. How much did Vincent give Ravi?


Thank you.

Hi,

For Q18, please see pg 604.

http://www.kiasuparents.com/kiasu/forum/viewtopic.php?f=69&t=280&start=6030

cheers

speedmaths.com

.

[superksmum]

speedmaths.com:

superksmum:

Hi, help needed for these questions from Catholic High SA 2011


Ques 18) at first, Ravi had $200 more than Vincent. He gave 40% of his money to Vincent. Vincent then gave 25% of his money to Ravi. In the end, Vincent had $68 more than Ravi. How much did Vincent give Ravi?


Thank you.

Hi,

For Q18, please see pg 604.

http://www.kiasuparents.com/kiasu/forum/viewtopic.php?f=69&t=280&start=6030

cheers

speedmaths.com

.

Hi speedmaths,

Thank you for the diverting.