Q&A - PSLE Math

[tianzhu]

jewelbox:

Hi, how do i solve this qn? thanks.

The ratio of the 3 sides of a right-angled triangle is 3:4:5. if the area of the triangle is 150 cubic cm, what is its perimeter?

Hi

Similar triangles are not covered in primary school maths syllabus.

So, I think a suitable way is \"Systematic Listing”.

It’s not too tedious in this case.

Ratio of 3 sides ------- 3:4:5

Use equivalent ratios, do a listing

Ratio of 3 sides ------- 15:20:25

This gives an area of 150 sq cm.

Hence, the perimeter is 60 cm

Best wishes

[mistychances]

Thank You, MathIzzzFun. Now, I know my mistake. Should hv just left them as fraction.


I’ve got another one here:

Question:
At first Alvin had twice as many trading cards as Steven. After Alvin had given away 285 of his trading cards, Steven had twice as many trading cards as Alvin. How many trading cards did they have altogether at first?

My working:
At first let Alvin -> 4u, so Steven will be 2u (altogether 6u at first)
After -> Alvin-1u, Steven-2u, so 285=3u
1u=285/3=95
Total 6u=570 –>My answer.

But the answer given was 845.

Appreciate your help once again.

[tianzhu]

mistychances:

But the answer given was 845.

Hi

Your answer of 570 is correct.

Best wishes

[Michaelia0816]

Pls help with this question from my HW, I do not know how to do?


1) a car and a coach travelled from town a to town b.the coach left town a a 0648 and 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 with the coach?

[Michaelia0816]

2) A car can only travel in the east or south direction. how many different ways can the car travel from point A to point B based on the following grids?

A_____ _____
||||
|||_____| B

Sorry, can’t scan the picture, too small! Dun be misunderstood it
The grids:
6 boxes with A on the top of the left while B is bottom of the right.
^
See above------------------|

[tianzhu]

Michaelia0816:

Pls help with this question from my HW, I do not know how to do?


1) a car and a coach travelled from town a to town b.the coach left town a a 0648 and 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 with the coach?

Hi

This question has been discussed before.

Best wishes

http://farm5.staticflickr.com/4149/4847914819_b35953e42b_z.jpg\">

[Michaelia0816]

Thx!

[Michaelia0816]

But I got more question, my teacher said it found in prelim too from recent exam!

[Michaelia0816]

Help this question

Web:
http://t.co/rLfIhEi6
Find the angle of angle S and T

[nounou]

Dear Tianzhu,


\"This gives 13 units (24-6-5) -------195\" -> why???
:?: Can you please explain where does 24 come from? What is 24?

Many thanks. :thankyou: :lovesite:

tianzhu:

Chan09:

Need help on this:
A car travel from X to Y at a speed 60km/h.
A van which started moving later than car travelled from Y to X at a speed 50km/h.
They met each other after the car had travelled 3/4 of the journey.
When car reached Y, the van is still 195km away from X.
What is the total distance between X and Y?

Ans: 360km.

Can I take that in 1 hour the car will cover 10km more ...but got stuck.

Hi

Would you like to share where is this question from?

A neat way to solve this question is to use inverse ratio.

Speed of car:Speed of van -------- 60:50 -------- 6:5
Distance travelled by car: Distance travelled by van --------- 6:5

Divide the distance line into 4 parts.

The car travelled 6 units and the van travelled 5 units during the same period.

This gives 13 units (24-6-5) -------195

1 unit ------- 15

Distance between X and Y ------- 24*15 ------- 360

Best wishes