Q&A - PSLE Math

[tweet]

ks2me:

Tweet,


http://i724.photobucket.com/albums/ww246/ks2me/P6MathairportBPzoo-1.jpg\">

Hi ks2me

Model is very clear cut, easy to understand.Thank you very much!

Best Regards
Tweet

[Vanilla Cake]

fxchow:

A 200m long MRT train took 20 min to pass through a tunnel completely.If the MRT train travelled at an average speed of 120m/min, find the length of the tunnel.

After the MTR train had emerged from the tunnel completely, length of the MRT train (200 m) itself had to be included.
120 x 20 = 2400 m (length of tunnel + train)
2400-200 = 2200 m

Length of tunnel is 2200 m

[fxchow]

Hi Vanilla Cake,


Thanks a lot!

So the answer provided is wrong :faint:

[tweet]

Here’s another question. Thank you for your time.


The ratio of the number of cows to the number of sheep in a farm is 4:9. 1/3 of the cows and 1/2 of the sheep are female. Find the ratio of the number of female cows to the number of female sheep. (Give your answer in the simplest form)

Many Thanks
Tweet

[kiasiparent]

tweet:

Here's another question. Thank you for your time.


The ratio of the number of cows to the number of sheep in a farm is 4:9. 1/3 of the cows and 1/2 of the sheep are female. Find the ratio of the number of female cows to the number of female sheep. (Give your answer in the simplest form)

Many Thanks
Tweet

female cows: female sheeps
4/3:9/2

Since the Lowest common factor is 6, multiply on both sides by 6
8:27

[suiyuan]

Thank you for your help.


A bus and a car travelled from Town X to Town Y. The bus left Town X at 10.48pm and it took 5 hours to reach Town Y. The car started 30 minutes later than the bus and it took 4 hours to reach Town Y. At what time did the car catch up with the bus?

[Vanilla Cake]

suiyuan:

A bus and a car travelled from Town X to Town Y. The bus left Town X at 10.48pm and it took 5 hours to reach Town Y. The car started 30 minutes later than the bus and it took 4 hours to reach Town Y. At what time did the bus catch up with the bus?

Hi suiyuan,

I think that there is a typographical error in your question. I interpret as \"At what time did the car catch up with the bus?\" Based on this assumption, here is the solution :

Bus
5 h -> Whole journey
1 h -> 1/5 journey
1/2 h -> 1/10 journey

Car
4 h -> Whole journey
1 h-> 1/4 journey

Difference in distance travelled in 1 h ->
1/4 - 1/5
=5/20 - 4/20
=1/20 of the journey

Time needed to catch up-> 1/10 divide by 1/20
1/10 x 20/1
= 2 h

Draw a timeline :
11.18 pm...............2 h ...............1.18 am

The car caught up with the bus at 1.18 am

Pls confirm if my answer is correct ?
Thks.

[kiasiparent]

Vanilla Cake:

suiyuan:

A bus and a car travelled from Town X to Town Y. The bus left Town X at 10.48pm and it took 5 hours to reach Town Y. The car started 30 minutes later than the bus and it took 4 hours to reach Town Y. At what time did the bus catch up with the bus?

Hi suiyuan,

I think that there is a typographical error in your question. I interpret as \"At what time did the car catch up with the bus?\" Based on this assumption, here is the solution :

Bus
5 h -> Whole journey
1 h -> 1/5 journey
1/2 h -> 1/10 journey

Car
4 h -> Whole journey
1 h-> 1/4 journey

Difference in distance travelled in 1 h ->
1/4 - 1/5
=5/20 - 4/20
=1/20 of the journey

Time needed to catch up-> 1/10 divide by 1/20
1/10 x 20/1
= 2 h

Draw a timeline :
11.18 pm...............2 h ...............1.18 am

The car caught up with the bus at 1.18 am

Pls confirm if my answer is correct ?
Thks.

correct.

[suiyuan]

Hi Vanilla cake


I’ll revised the question to correct error.Your answer is correct.
Thank you

[mathsparks]

I’ve a question on calculation of carpark charges. A man drives his car into carpark A at 4:30pm and leaves at 6:30pm. How much does he have to pay if the carpark charges $1 an hour or part thereof and $3 per entry after 5pm.


The answer could either be:
1) $1 (first half hr) + $3 (per entry) = $4

or
2) $1x2 (2 hrs) = $2

Since different carparks in SG calculate differently, both answers should be accepted.

Any comments?