Q&A - PSLE Math

[Dharma]

This one is not exacty on rate or average …a non routine type


It is a dark and stormy night. Four people must evacuate from an island to the mainland. The only link is a narrow bridge which allows passage of two people at a time. Moreover, the bridge must be illuminated, and the four people have only one lantern among them. After each passage to the mainland, if there are still people on the island, someone must bring the lantern back. Crossing the bridge individually, the four people take 2, 4, 8 and 16 minutes respectively. Crossing the bridge in pairs, the slower speed is used. What is the minimum time for the whole evacuation?

[tianzhu]

Dharma:

This one is not exacty on rate or average ...a non routine type


It is a dark and stormy night. Four people must evacuate from an island to the mainland. The only link is a narrow bridge which allows passage of two people at a time. Moreover, the bridge must be illuminated, and the four people have only one lantern among them. After each passage to the mainland, if there are still people on the island, someone must bring the lantern back. Crossing the bridge individually, the four people take 2, 4, 8 and 16 minutes respectively. Crossing the bridge in pairs, the slower speed is used. What is the minimum time for the whole evacuation?

Hi Dharma

The dark and stormy night reminds me of the destruction caused by Typhoon Morakot, very scary indeed.

Good and creative question, but will keep this for my son to do after his PSLE exam.This will keep his backside glued to the chair for a little while longer.

Best Wishes

[Dharma]

tianzhu:

The dark and stormy night reminds me of the destruction caused by Typhoon Morakot, very scary indeed.

Good and creative question, but will keep this for my son to do after his PSLE exam.This will keep his backside glued to the chair for a little while longer
.
Best Wishes

That's a good one!

[tianzhu]

Hi Dharma


It’s 30 minutes.

Life can be drastically changed in a matter of seconds not even minutes.

Best Wishes

[Dharma]

tianzhu:

Hi Dharma


It's 30 minutes.

Life can be drastically changed in a matter of seconds not even minutes.

Best Wishes

Just by using the right strategy, you've saved the 4 guys

[Vanilla Cake]

Hi,

I am Pandan Cake (VC's younger sister) using her ID to post 3 rate questions and 1 speed question. Need your time and help to solve them so that I can forward them (solutions) to one of my elder cousins (a P6 boy) who is taking PSLE this year. Thanks in advance.
:please:

Q1
Desmond takes 9 days to renovate 1 kitchen while Philip takes 21 days to renovate the same kitchen. If Philip starts renovating the kitchen first and leaves the rest to be completed by Desmond, they will take 13 days in total to complete renovating the kitchen. How many days does Desmond spend on the job?

Q2
When Katie spent 1 day and Mia spent 2 days painting, they would paint 11/12 of a house. On the other hand, when Mia spent 5 days and Katie spent 2 days painting, they would paint 2 & 1/6 houses. How long will each of them need to paint 1 whole house by themselves?

Q3
When Caleb spent 2 days and Ethan spent 3 days assembling computers, they produced 42 sets of PCs. When Caleb spent 4 days and Ethan spent 2 days assembling computers, they produced 44 sets of PCs. How long will each boy require to assemble 30 sets of computers?

Q4
Nicholas and Oliver started driving from the same point but in the opposite directions round a 15 km circular track. Nicholas took 10 minutes t o complete each round. The two drivers met each other after 6 minutes. (a) At what speed where Nicholas ands Oliver driving at ? Give your answer in km/h. (b) How many rounds would each driver have completed when they met each other at the starting point for the second time ?

[Dharma]

Vanilla Cake:

Hi,

I am Pandan Cake (VC's younger sister) using her ID to post 3 rate questions and 1 speed question. Need your time and help to solve them so that I can forward them (solutions) to one of my elder cousins (a P6 boy) who is taking PSLE this year. Thanks in advance.
:please:

Q1
Desmond takes 9 days to renovate 1 kitchen while Philip takes 21 days to renovate the same kitchen. If Philip starts renovating the kitchen first and leaves the rest to be completed by Desmond, they will take 13 days in total to complete renovating the kitchen. How many days does Desmond spend on the job?

Earlier mistake corrected

http://www.postimage.org/

[Dharma]

Vanilla Cake:

Hi,

I am Pandan Cake (VC's younger sister) using her ID to post 3 rate questions and 1 speed question. Need your time and help to solve them so that I can forward them (solutions) to one of my elder cousins (a P6 boy) who is taking PSLE this year. Thanks in advance.
:please:

Q2
When Katie spent 1 day and Mia spent 2 days painting, they would paint 11/12 of a house. On the other hand, when Mia spent 5 days and Katie spent 2 days painting, they would paint 2 & 1/6 houses. How long will each of them need to paint 1 whole house by themselves?

http://www.postimage.org/

[Dharma]

Vanilla Cake:

Hi,

I am Pandan Cake (VC's younger sister) using her ID to post 3 rate questions and 1 speed question. Need your time and help to solve them so that I can forward them (solutions) to one of my elder cousins (a P6 boy) who is taking PSLE this year. Thanks in advance.
:please:


Q3
When Caleb spent 2 days and Ethan spent 3 days assembling computers, they produced 42 sets of PCs. When Caleb spent 4 days and Ethan spent 2 days assembling computers, they produced 44 sets of PCs. How long will each boy require to assemble 30 sets of computers?

http://www.postimage.org/

[Dharma]

http://www.postimage.org/


Hope these are useful. Good luck