Q&A - PSLE Math

[CDE]

MathIzzzFun:

jarenchuatw:

Help! How to solve this question?


A tank is 2/3 filled with water. It took 16minutes for a tap to drain this water completely. Another tap could fill the tank in 12 minutes when empty. If both the taps were turned on together, how long would it take for the tank to be completely filled with water?

Thanks in advance

Hi

Tank capacity --> 24 units
1st tap drain rate --> 2/3 x 24 units/16 min = 1 unit/min
2nd tap fill rate --> 24 units/ 12 min = 2 units/min
When both taps are turned on, nett fill rate --> 1 unit/min
2/3 tank filled, so 1/3 to fill --> 8 units to be filled
time taken to fill to full --> 8 units / 1 unit/min = 8 min

cheers.

MathIzzzFun, how do you get 24 units of tank capacity? It's not stated in question.

[tianzhu]

superhappy:

Michaelia0816:

Thx, Tianzhu, it is from PSLE Booklet, which my HW.

Hi, I need help on this question.

A rectangular tank was filled with water flowing from the tap.
At 10am, the tank was empty.
At 1pm, the tank was 1/3 filled with water.
At what time would the tank be 7/12 filled with water flowing from the tap.

Thank you

Hi

Good Morning.

I think this is a MCQ question.

A common multiple of 3 and 12 is 12.

1/3 filled ------ 4 units (1/3*12)

At 1pm ------- 4 units filled with water.

3h (180 minutes) ------- 4 units

45 minutes ------- 1 unit

135 minutes ------ 3 units (1/3 to 7/12)

From 1pm, add a duration of 135 minutes, I’ll leave it to students to work out the answer.

Best wishes

[tianzhu]

CDE:

Hi, can anyone g ive the explanation & working on the following:


A rectangle divides a plane into 2 region at the most. How many regions at the most can 5 such identical rectangles divide the plane into?

No picture or anything else given. The answer is 82 regions, but how :?
TIA.

Hi

Where is this question from?

I get an answer of 16(dividing the plane into regions).

Best wishes

[2DMommy]

Please help me with the two questions :


1) Mr Tan bought some thumbs drives for $340. If he was given 15% discount, he would be able to buy 4 more identical thumb dirves for the same amount of money. What was the original price of each thumb drives ?

2) Mr and Mrs Lim travelled in opposite directions after leaving their house at the same time. Mr Lim travelled towards Ponggol while Mrs Lim travelled towards Jalan Elias. Mrs Lim drove at a speed which was 12km/h slower than Mr Lim. After 25 min, Mr Lim had to turn back towards home for his misplaced keys while Mrs Lim continued with her journey to Jalan Elias without stopping. At 9am, the distance between Mr and Mrs Lim was 16 km. How far was Mrs Lim from her home at 9am?

Thank you !

[tianzhu]

2DMommy:

Please help me with the two questions :

1) Mr Tan bought some thumbs drives for $340. If he was given 15% discount, he would be able to buy 4 more identical thumb dirves for the same amount of money. What was the original price of each thumb drives ?

Hi

Amount saved by Mr Tan due to 15% discount ------- 15/100*340 ------- 51

With this amount, he’ll be able to buy 4 thumb drives @15%discount.

Discounted price of each thumb drive ------- 51/4 ------ 12.75

Original price per thumb drive ------ 12.75/0.85 ------- 15

Best wishes

[Michaelia0816]

Pls help with this too!

http://t.co/wf2cfrbz
And
1) A jar filled with 40 identical screws weighs 1.4 kg. The same jar when filled with 20 identical nails weighs 500 g. The mass of each screw is twice the mass of each nail. What is the mass of the empty jar?

[tianzhu]

Michaelia0816:

1) A jar filled with 40 identical screws weighs 1.4 kg. The same jar when filled with 20 identical nails weighs 500 g. The mass of each screw is twice the mass of each nail. What is the mass of the empty jar?

Hi

You may use MD or work with units.

J + 80u ----- 1400

J + 20u ----- 500

60u ------ 900

20u ------ 300

J + 300 ------ 500

J ----- 200g (mass of empty jar)

Best wishes

[tianzhu]

Michaelia0816:

Pls help with this too!

http://t.co/wf2cfrbz

Hi

If I am not wrong, Q1 is in your PSLE five years series.

Please refer to the solution.

Best wishes

[Michaelia0816]

I do not have the solutions!

[tianzhu]

Michaelia0816:

I do not have the solutions!

Hi girl

Do you really need help to solve this question? Or you just want to check the answer?

Area of triangle DFC ------ ½*10*7.2 -------- 36

Area of EGCD ------ 5/9*36 ------- 20

Area of ABCD ------- 20*6/5 ------- 24

AD -------- 24/10 ------- 2.4

Best wishes