Q&A - PSLE Math

[small]

MathIzzzFun:

small:

Another speed question, please help and TIA..


Question:
An oil tanker, which left Town X for Town Y, travelled at an average speed of 50 km/h. A car, which left Town X some time later, managed to overtake the oil tanker after travelling 4/9 of the distance between towns X and Y. From then, the car took 4 and 2/5 hours to reach Town Y. If the oil tanker was 30 km away when the car reached Town Y, how long did the oil tanker take to travel from Town X to Town Y?

Hi
Time taken for oil tanker to travel 5/9 of the distance = 22/5 + 30/50 = 5h
Time taken for oil tanker to travel from X to Y = 9/5 x 5 = 9h

cheers.

Huge thanks MathIzzzFun...

[MathIzzzFun]

small:

MathIzzzFun:

[quote=\"small\"]Another speed question, please help and TIA..


Question:
An oil tanker, which left Town X for Town Y, travelled at an average speed of 50 km/h. A car, which left Town X some time later, managed to overtake the oil tanker after travelling 4/9 of the distance between towns X and Y. From then, the car took 4 and 2/5 hours to reach Town Y. If the oil tanker was 30 km away when the car reached Town Y, how long did the oil tanker take to travel from Town X to Town Y?

Hi
Time taken for oil tanker to travel 5/9 of the distance = 22/5 + 30/50 = 5h
Time taken for oil tanker to travel from X to Y = 9/5 x 5 = 9h

cheers.

Huge thanks MathIzzzFun...[/quote]u r welcome

have a great week !

cheers.

[tianzhu]

small:

Tianzhu,

Once again many thanks..

Hi

Good Morning.

You're welcome.

Best wishes

[keinic]

Hi


Would greatly appreciate if someone could help with the following question:

Tank X contained 40L of petrol at first. Tank Y, which is empty, fills at a rate of 26.7L per minute for 4 minutes before the tap filling tank X is turned on. Tank X fills at a rate of 18.5L per minute. Petrol is leaking from the bottom of Tank Y at a rate of 1.2L per minute.

a. How much petrol is in Tank Y 1 minute after the tap in Tank X is turned on ?
b. How long will it take for Tank Y to contain 146L more petrol than Tank X?

Tks.

[small]

keinic:

Hi


Would greatly appreciate if someone could help with the following question:

Tank X contained 40L of petrol at first. Tank Y, which is empty, fills at a rate of 26.7L per minute for 4 minutes before the tap filling tank X is turned on. Tank X fills at a rate of 18.5L per minute. Petrol is leaking from the bottom of Tank Y at a rate of 1.2L per minute.

a. How much petrol is in Tank Y 1 minute after the tap in Tank X is turned on ?
b. How long will it take for Tank Y to contain 146L more petrol than Tank X?

Tks.

Hi.

HTH..

a) 1 minute after the tap in Tank X is turned on means TanK Y was filled for 5 minutes.

Tank Y ---- 5 x (26.7-1.2) = 127.5 litres

b)
Before tap on for Tank X, Tank Y was on for 4 mins:
Volume difference between Tank Y and Tank X ----- (25.5 x 4) - 40 = 62 litres

We will need to fill up the gap between Tank X and Tank Y, so when Tank Y is 146 litres more than Tank X, the gap is :

146 - 62 = 84 litres

After tap on for Tank X :
Volume difference between Tank X and Tank Y in every 1 minute ----- (25.5 - 18.5) = 7 litres

84 / 7 = 12 mins

[keinic]

small:

Hi.

HTH..

a) 1 minute after the tap in Tank X is turned on means TanK Y was filled for 5 minutes.

Tank Y ---- 5 x (26.7-1.2) = 127.5 litres

b)
Before tap on for Tank X, Tank Y was on for 4 mins:
Volume difference between Tank Y and Tank X ----- (25.5 x 4) - 40 = 62 litres

We will need to fill up the gap between Tank X and Tank Y, so when Tank Y is 146 litres more than Tank X, the gap is :

146 - 62 = 84 litres

After tap on for Tank X :
Volume difference between Tank X and Tank Y in every 1 minute ----- (25.5 - 18.5) = 7 litres

84 / 7 = 12 mins

Hi small

Thanks so much for the detailed explanation. Initially, my own answer worked out for part b. was 16 mins i.e. 4mins + 12 mins, as I thought we had to include the 4 mins that Tank Y was turned on which contributed to the 62 litres difference . However, the model answer given was also 12 mins, the same as what you've worked out. I do agree with the answer now after looking at your detailed solution.
Thanks very much for your help. Cheers!

[small]

Hi Keinic,


You are welcome.

[beanbear]

Hi Can someone provide a model method for the following problem sum. I also have a question regarding the interpretation of certain words in the question.


4 children shared a box of chocolate bars. The first child took 1/2 of the total bars of chocolate and 1/2 of a chocolate bar. The second child took 1/2 of the remaining bars and 1/2 of a chocolate bar. The third child took 1/2 of the remaining bars and 1/2 of a chocolate bar. The fourth child took the remaining 7 bars.
(A) How many bars of chocolate were there? Ans key: 63
(B) How many bars of chocolate did the third child get? Ans key: 8

As I was working through, I was wondering about what to do with the 1/2 chocolate bar after the 1st child. Does the remaining 1/2 chocolate bar go to the remaining amount? Do you interpret \"the remaining bars\" as \"whole bars\" only or include the half choc bar?

[match3frog]

Hi mathizzzfun and yomamas, thank you for the solutions! Have a nice day

[tianzhu]

Hi


Use \"Work backwards\"

Hope this helps.

Best wishes

http://farm8.staticflickr.com/7061/7083155463_e42680a404_z.jpg\">