Tutor MathsGuru: Ask me for your burning Maths questions!

[Vanilla Cake]

YLH88:

3) Car A and Car B left Town Y at the same time, heading in the opposite direction.Car A headed for Town Z while Car B left for Town X.The speed of Car B was 20 km/h faster than Car A. After 1/2 h, Car A had completed 2/3 of its journey while Car B had completed 1/2 of its journey.The two cars were also 110 km apart.

a) Calculate the speed of Car A.
b) How far was Car B from Town X when Car A reached its destination ?

Vanilla Cake:

½ of distance between Town X and Town Y = (110+10)÷2=60 km
⅔ of distance between Town Y and Town Z = 60-10 = 50 km
Since Distance travelled in ½ h = 50 km,
(a) Constant speed of Car A = 50x2 = 100 km/h

Distance between Town Y and Town Z = 50/2x3 = 75 km
Time taken for Car A = 75÷100 = 3/4h
Distance drove by Car B in 3/4h = 3/4x(100+20) = 3/4x120 = 90 km
Distance between Town X and Town Y = 60x2 = 120 km
120-90 = 30 km
(b) Car B was 30 km from Town X when Car A reached its destination.

Hope someone can forward with a pictorial distance-time travel diagram and easier method to help you.
May I know where are all these 7 speed questions taken from?

Hi YLH88,
http://psle2010a.blogspot.com/2010/06/speed-p6_12.html to help you understand better.

[YLH88]

Hi VC,


Thank you for the solution. These are from his school worksheets for the holiday… He has no choice but to do because his mummy very kiasu and worried about his PSLE.

Thank you!!

[Herbie]

I have one qn.


Singapore Hokkien Huay Kuan Paper 2 2009, Q 17.

In a school science fair, there were exhibits fom Pr 4 to 6. Altogether 25 exhibits came from P5 and 6. If 16 exhibits were not from P6 and 15 exhibits were not from P5, how many wxhibits were there altogether?

Kindly advise.

Many thanks!

[Vanilla Cake]

Herbie:

I have one qn.


Singapore Hokkien Huay Kuan Paper 2 2009, Q 17.

In a school science fair, there were exhibits fom Pr 4 to 6. Altogether 25 exhibits came from P5 and 6. If 16 exhibits were not from P6 and 15 exhibits were not from P5, how many wxhibits were there altogether?

Kindly advise.

Many thanks!

Quick answer:

P5+P6=25
P4+P5=16
P4+P6=15

2P4+2P5+2P6=25+16+15=56
P4+P5+P6=56/2 =28

Altogether, there were 28 exhibits

[YLH88]

Hi VC,


Thank you so much for all the solutions !! Your reply is super fast

As mentioned above, all these 7 questions are from his school worksheets on Speed topic. They are so tough …

Don’t worry, with such a helpful and caring big sister like you, I’m sure your younger sister will do well in her PSLE next year too !!

Regards

[Almighty]

[/quote]Hi Almighty,


You must be careful with this word \"more\"
When we say Ahmad has 3 times more stamps than Ali, it means Ahmad has 4 parts and Ali 1 part. This more is applied between Ahmad and Ali, so Ahmad has xxx stamps more than Ali.

In that question you posed, the total is given as a finite salary. So a fraction more of the salary spent has to be confined within the salary amount and cannot be interpreted to go beyond the amount. So it cannot go more than the salary. GWIM?[/quote]

Thankyou very much Ksi. I will remember this in future.

[Almighty]

Hi Vaniila cake,


Wish i had a Big sister like u!!! I hv a dobt reg yr answer for this problem:
\"Wei Qiang walked up a flight of steps at an average speed of 50 m/min.
When he reached the top, he ran down the same flight of steps at a speed of 200 m/min. If he took a total of 1 min to walk up and run down, how many seconds did he take to walk up the flight of steps ?\"

Ratio of time
4 : 1
Multiply by 4( Must be by 12 right? )
48 : 12

(48+12)min= 60 min ie he took a total of 1 min to walk up and run down
5u = 60 seconds
(I dint get how u interpretated 60 min n then say 1 min .I think it sh b (48 + 12) Secs = 60 Secs= 1min.But how can it b (48+12) secs as ratio of time in 4:1 is in min.
Can u please clarify?

[CoffeeCat]

almighty, I think it’s just a typo. What she meant is using the ratio of time, wei qiang will took 48 secs to walk up and 12 secs to run down. The units are not crucial because ratios are dimensionless.

[Vanilla Cake]

CoffeeCat:

almighty, I think it's just a typo. What she meant is using the ratio of time, wei qiang will took 48 secs to walk up and 12 secs to run down. The units are not crucial because ratios are dimensionless.

Thanks, CoffeeCat.


Hi Almightly,
I have revised the workings to make it clear.Was in a rush and didn't check thoroughly.

[Almighty]

Hi vanilla cake,

Thanks for your reply.But my doubt was, Ratio of time is in min or seconds?Since the question says:average speed of 50 m/min and 200 m/min.I did the Ratio of time in minutes and got stuck.Pl clarify how u made ratio of time in secs.