Q&A - PSLE Math

[liketoeat]

Vanilla Cake:

liketoeat:

[quote=\"Vanilla Cake\"]
Sure and you may wish to help us back by telling where is the source of this question? Which school, assessment book, tuition centre etc?

Roysth 2009 P6 CA1 Paper 2 Q17

Hi liketoeat,

Roysth 2009 P6 CA1 Paper 2 Q17:
Jerrick and Edan each bought a number of trading cards.Jerrick gave away 1/12 of his trading cards to Edan and had 165 cards left.
(a) How many trading cards did Jerrick give Edan?
(b) If the number of cards given to Edan was 1/3 of what Edan had, find the number of cards Edan had at first.
(c) After receiving the cards from Jerrick, Edan gave 2/5 of his cards to Jerrick.Find the ratio of the number of cards Jerrick had after this to the total number of cards bought by the two boys.

From cbox, I got the info that the exact source of this cookie question was from Rosyth School P6 SA1 2009 Paper 2 Q17.
Thanks.[/quote]so sorry, must have seen wrongly.

[musette]

Hi,


Can somebody please show me the working for this question?

From Singapore Hokkien Huay Kuan schools, 2009 Prelim, Paper 2 Q15

A car and a coach travelled from Town A and Town B. The coach left Town A at 0648 and it took 5 hours to reach Town B. The car started 30 minutes later than the coach and it took 4 hours to reach Town B. At what time did the car catch up to the coach?

I just can't solve this without using algebra and simultaneous equations.

Thank you!

[corneyAmber]

http://i724.photobucket.com/albums/ww246/ks2me/P6Mathtradingcards-1.jpg\">

[Vanilla Cake]

musette:

A car and a coach travelled from Town A and Town B. The coach left Town A at 0648 and it took 5 hours to reach Town B. The car started 30 minutes later than the coach and it took 4 hours to reach Town B. At what time did the car catch up to the coach?

Constant distance
Ratio of time
Car : Coach
4 : 5

Ratio of speed
Car : Coach
5 : 4

Difference in speed = 1u
Since the coach left Town earlier by 1/2 hour, distance travelled = 1/2x4u=2u
Time taken for car to catch up for this distance = 2u/1u= 2 hours
Time for car to catch up with the coach -> Add 2 hours + 1/2 hour to 0648 = 0918

OR

Assume distance between Town A and Town B be D
Constant speed of coach = D/5 = 0.2D
Constant speed of car = D/4 = 0.25D
Difference in the constant speed of car and coach = 0.25D-0.2D=0.05D

Distance travelled by the coach in 1/2 hour earlier = 1/2x0.2D=0.1D
Time taken for car to catch up = 0.1D/0.05D= 2 hours

0648......+1/2h......+2h.............0918
The car caught up with the coach at 0918

OR

LCM of 4 and 5 is 20.Distance between the 2 towns are 20 units
Coach: 5 hours for 20 units ie 1 hour for 4 units
Car: 4 hours for 20 units ie 1 hour for 5 units

Comparing, car travelled 1 more unit than the coach in 1 hour .
Since the coach started 1/2 hour earlier, headstart = 1/2x4units = 2 units
So, the car needed to catch up with this 2 units that it lost.

Car caught up by a unit in 1 hour
2 units will need 2 hours
meaning the car needs 2 hours to catch up with the coach.

0648......+1/2h......+2h.............0918
The car caught up with the coach at 0918

OR

Refer to http://prischoolmaths.blogspot.com/2009/09/combined-hokkien-speed-question.html

[Dharma]

musette:

Hi,


Can somebody please show me the working for this question?

From Singapore Hokkien Huay Kuan schools, 2009 Prelim, Paper 2 Q15

A car and a coach travelled from Town A and Town B. The coach left Town A at 0648 and it took 5 hours to reach Town B. The car started 30 minutes later than the coach and it took 4 hours to reach Town B. At what time did the car catch up to the coach?

I just can't solve this without using algebra and simultaneous equations.

Thank you!

Time ratio => Coach : Car = 5:4
Speed ratio => Coach : Car = 4:5
Distance travelled by coach in 1/2hr
= 4u x 1/2
= 2u

Time taken for to catch up with coach
= 2u/(5u-4u)
= 2hrs

2 hrs after car left Town A
= 0918 or 9.18am

[Dharma]

liketoeat:

Hi, I don't know if this question is appropriate for P6 but my niece received it as her homework from her school teacher.


Toy Train A and Toy Train B are 15 m apart from each other. When the toy trains moved towards each other, they would meet in 5 min. However, if the toy trains moved in the same direction, toy Train A would overtake Toy Train B in 5/12 h. Find the speed of Toy Train A and Toy Train B.

Speed of train A + Speed of train B = 15m/5min = 3m/min
Speed of train A - Speed of train B = 15m/25min = 0.6m/min
Speed of train A = (3.6/2)m/min = 1.8m/min
Speed if train B = 1.2m/min

[musette]

Thank you VC and Dharma for the solution! Really appreciate it.

[liketoeat]

Thank you, Dharma…I’ll need some time to understand the solution.

[Dharma]

liketoeat:

Thank you, Dharma....I'll need some time to understand the solution.

Hi liketoeat,

Time reqd to meet = Distance apart/Sum of Speeds of trains

Time reqd to catch up = Distance apart/ Diff in Speeds of trains

[liketoeat]

Dharma:

liketoeat:

Thank you, Dharma....I'll need some time to understand the solution.

Hi liketoeat,

Time reqd to meet = Distance apart/Sum of Speeds of trains

Time reqd to catch up = Distance apart/ Diff in Speeds of trains

oh yes, got it. Thanks again.