Q&A - PSLE Math

[MathIzzzFun]

Suz855:

Need help with following speed qns


Q1) A car started travelling from Town A to Town B at 9a.m. At the same time, the lorry started travelling from Town B to Town A. The car had a speed of 20km/h faster than the lorry. The car passed the lorry 45km away from the midpoint. Given that the car reached Town B at 3p.m., what time would the lorry reached Town A? :?

Q2) At 11a.m., Mr T left from Town X & drove towards Town Y at an ave speed of 80km/h. 15 min later, Mr R left Town Y and drove along the same route as Mr T towards Town X. After travelling 120km, Mr R passed Mr T.
a) What was the ave speed at which Mr R travelled?
b) How far apart were there at 3.20p.m.? Express your answer as a fraction.
:sad: :imdrowning: :frustrated:

Thanks

Q1- The car reached Town B at 3 pm or 5 pm ?
If the car reached at 3 pm, then the speeds for car and lorry are not realistic --> 30 km/h for car and 10 km/h for lorry.

Q2 - is the question complete ? any info left out - eg, at what time did Mr T and Mr R pass each other ? or Mr R is also travelling in the same direction ie from X to Y?

cheers.

[YumYum]

tianzhu:

YumYum:

Hi Tianzhu,

Thank you for compiling the 'If' questions, they are very useful. thks for yr kind thoughts. :thankyou:

Hi YumYum

Good Morning.

You're welcome.

Wishing you all the best for PSLE 2013.

Best wishes

Tianzhu: do you have the working solution for the \"if\" series Qns? Stuck for Qn 2 and 4...and pie-seh if need to ask for other Qns ...thanks!

[iCreative Math]

Suz855,


I believe you are correct in both instances.

For Q1, the answers, based on the facts in the question, are 30 km/hr for the speed of the car, and 10 km/hr for the speed of the lorry. Agree with you that both the speeds are not very realistic.

For Q2, the question is indeed incomplete. Based on the facts given, there are many possibilities. For example, if the distance between the two towns is 380 km, the average speed of Mr R would be 40 km/hr. If the distance is 460 km, then the average speed of Mr R would be 30 km/hr.

Best Regards,

iCreative Math

[tianzhu]

Suz855:

Need help with following speed qns


Q1) A car started travelling from Town A to Town B at 9a.m. At the same time, the lorry started travelling from Town B to Town A. The car had a speed of 20km/h faster than the lorry. The car passed the lorry 45km away from the midpoint. Given that the car reached Town B at 3p.m., what time would the lorry reached Town A? :?

Hi

Is this question from the past years papers?

Hope this helps.

Best wishes

http://farm9.staticflickr.com/8120/8679216577_5c3090f398_z.jpg\">

[tianzhu]

YumYum:

Tianzhu: do you have the working solution for the \"if\" series Qns? Stuck for Qn 2 and 4...and pie-seh if need to ask for other Qns ...thanks!

Hi

Please check your PM.

I've sent the solution for Q4 to you.

Best wishes.

[Suz855]

I copy these questions word for word, they are from an assessment book so pls do not be too bother, thks everyone for the help.


Q1- The car reached Town B at 3 pm or 5 pm ?
If the car reached at 3 pm, then the speeds for car and lorry are not realistic –> 30 km/h for car and 10 km/h for lorry.

Q2 - is the question complete ? any info left out - eg, at what time did Mr T and Mr R pass each other ? or Mr R is also travelling in the same direction ie from X to Y?

cheers.[/quote]

[wahwah]

Hi all,

Need help with the following question. Many thanks in advance.

Alex gave 40% of his angelfish to Peter. After that 15 of Alex’s angelfish died. He then gave 1/3 of the remaining angelfish to Peter. As a result, the ratio of Alex’s angelfish to Peter’s angelfish became 4:7. How many angelfish had Alex at first?

[tianzhu]

wahwah:

Hi all,

Need help with the following question. Many thanks in advance.

Alex gave 40% of his angelfish to Peter. After that 15 of Alex's angelfish died. He then gave 1/3 of the remaining angelfish to Peter. As a result, the ratio of Alex's angelfish to Peter's angelfish became 4:7. How many angelfish had Alex at first?

Hi

Good Morning.

This question is crafted in such a way that it is pretty neat to use MD.

Due to time constraints, I’ll be giving some pointers.

Draw a bar; divide into 4 units to show Peter (40%), and remaining 6 units.

Subdivide 15 into 3 smaller boxes of 5 each, remainder of 3 groups of (2 units - 5) ----- 1/3 given to Peter and 2/3 to Alex

And, in the end, we have,

Peter -------- 4 units + 2 units – 5 -------- 6 units – 5
Alex --------- 4 units – 10

As a result, the ratio of Alex's angelfish to Peter's angelfish became 4:7.

4 units – 10: 6 units – 5 ------ 4:7

28units – 70 -----24units – 20

1 unit ------ 12.5

Number of angelfish@first -------125

Best wishes

[wahwah]

Hi tianzhu,

Thanks a lot for the solution.

[CloudeeDaz]

tianzhu:

Good Morning.

This question is crafted in such a way that it is pretty neat to use MD.

Number of angelfish@first -------125

Best wishes

thank you ,tianzhu!
You made it seemed so simple!

......and to think that i acually spend some time last night trying (unsuccessfully )to work it out! :oops: :oops:

@wahwah thanks for the question!