Q&A - PSLE Math

[php]

ozora:

ozora:

help needed. looks simple but my answer is fraction which must be wrong.

Tom had 295 more sweets than John.
After Tom gave away 2/5 of the sweets he had and John gave away 2/3 of the sweets, Tom had 329 more sweets than John.
how many sweets did they have altogether at first?

I redo the model.
is Tom's sweets = 523
and John's sweets = 228.
can anyone check if my answer is correct.

Using LCM 5,3 i.e. 15

Before
Tom -> 15units + 295
John -> 15units

Gave Away
Tom -> 2/5 (15units + 295) = 6units + 118
John -> 2/3 (15units) = 10units

Left
Tom -> 15units+295-6units-118 = 9units + 177
John -> 15units - 10units = 5 units

9units+177 - 5units = 329
4units = 152
1unit = 38

15units+295+15units = 38x30 + 295 = 1435

[MathIzzzFun]

YumYum:

Hi, one more Qn:


Derrick and John shared a sum of money.
Derrick received 2/7 of the sum of money.
Both of them spent part of their money and saved the rest.
The amount of money Derrick spent was 3/5 the amount he saved.
The amount of money John spent was 1/9 the amount he saved.
Express the amount of money Derrick spent as a ratio of the amount John saved. thks!

Derrick's money : John's money = 2 : 5 --> 8u : 20u

Derrick's spending : Derrick's savings --> 3u : 5u
John's spending : John's savings --> 2u : 18u

Derrick's spending : John's savings = 3u : 18u = 1 : 6

cheers.

[ozora]

php:

ozora:

[quote=\"ozora\"]help needed. looks simple but my answer is fraction which must be wrong.

Tom had 295 more sweets than John.
After Tom gave away 2/5 of the sweets he had and John gave away 2/3 of the sweets, Tom had 329 more sweets than John.
how many sweets did they have altogether at first?

I redo the model.
is Tom's sweets = 523
and John's sweets = 228.
can anyone check if my answer is correct.

Using LCM 5,3 i.e. 15

Before
Tom -> 15units + 295
John -> 15units

Gave Away
Tom -> 2/5 (15units + 295) = 6units + 118
John -> 2/3 (15units) = 10units

Left
Tom -> 15units+295-6units-118 = 9units + 177
John -> 15units - 10units = 5 units

9units+177 - 5units = 329
4units = 152
1unit = 38

15units+295+15units = 38x30 + 295 = 1435[/quote]Saw my mistakes. thanks

[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

[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]