Q&A - PSLE Math

[Michaelia0816]

Still got 17 question!!

[tianzhu]

Michaelia0816:

If Tianzhu,

I got a another question again
Also having difficulties to complete it!
Do the part b one only, I have solved the first one!

Amy and Cindy set off from Town X for Town Y at 1pm., at the uniform speeds of 70km/h and 85km/h respectively?
A) how long did it take for them to be 45km apart? The answer is 3h!
I'd Amy arrived in Town Y at 5.15pm, at what time would Cindy arrived there?

Hi

Use inverse ratio

Speed
Amy:Cindy -------- 70:85 ------- 14:17

Time
Amy:Cindy -------- 70:85 ------- 17:14

17 units ------- 255 minutes
14 units -------- 14*15 -------- 210 minutes ------- 3.5h

3.5h from 1 pm --------- 4.30 pm.

Best wishes

[tianzhu]

Michaelia0816:

Roger took 1/1/3 h to drive from Greenland to pinkcity at an average speedof 60km/h. After this, he increased his speed by 25% and continued driving to redsville for 40 minutes.

A) how far did Roger drive together?
B) find his average speed for the whole journey?

Hi

From GL to PC

60*4/3 ------ 80 km

Increased speed -------- 60*1.25 ------- 75

Distance from PC to R ------ 75*2/3 ------ 50 km

Roger covered (80+50) --------- 130 km

Time taken ------- 4/3 + 2/3 ------ 2h

Average speed -------- 130/2 ------- 65 km/h

Best wishes

[Michaelia0816]

Thank you again and for your hard work

,

[Michaelia0816]

What is inverse ratio?

[Michaelia0816]

Anyway, thank you for all the questions you helped me!

[Michaelia0816]

Michaelia0816:

7)Car x, car y and car z together crossed point a at noon as they were heading for point b. by 1.30 pm, car x was 75 km from point a and car y was ahead of car x by 6km. By this time, car x had already travelled the combined distance of the other two cars from point a. What was the difference in speed between car z and y?

Can Tianzhu help out with this question, you seemed to missed it!

[tianzhu]

Michaelia0816:

7)Car x, car y and car z together crossed point a at noon as they were heading for point b. by 1.30 pm, car x was 75 km from point a and car y was ahead of car x by 6km. By this time, car x had already travelled the combined distance of the other two cars from point a. What was the difference in speed between car z and y?

Hi

Please check.

Best wishes

[tianzhu]

Michaelia0816:

What is inverse ratio?

Hi

Please go to page 540.

It’s time of the year again when the topic on “Speed” will be covered in the school syllabus.

If you refer to the PSLE Maths thread, the term inversely proportional or inverse proportion has been mentioned regularly when dealing with Speed questions.

Inverse proportion is covered in Secondary Two syllabus. However, I believe many schools are introducing such concept to selected classes.

It is worthwhile to spend a bit of time understanding this concept as it’ll give students a different approach.

It’s not too difficult to grasp it. When travelling a certain distance, if you travel at a faster speed, you will take a shorter time to reach your destination. Speed increases, Time decreases. Speed decreases, Time increases.

You may apply the inverse proportion concept on these questions.

Ben cycles from his home to the church every Sunday. If he were to cycle at 10km/h, he would reach the church at 3pm. If he were to cycle at 15km/h, he will reach there at 1pm. a) how far does Ben have to cycle from his home to the church? b) at what average speed must he cycle if he wants to reach the church at 2pm?

Ann is driving to a destination. If she travels at 80km/h, she would be 20min late. If she travels at 60km/h, she would be 45 min late. How long will journey take if she travels at 90km/h.

Best wishes.

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[tianzhu]

superksmum:

Hi help needed!


A tank was half filled with water. More water was added until it was 2/3 full. The ratio of the mass of the tank when it was 1/2 full to the mass of the tank when it was 2/3 full was 7:9.

a) What is the ratio of the volume of water in the tank when it was 1/2 full to the volume of the water went he tank was 2/3 full?

b) the mass of the empty tank was 500g. What was the total mass of the tank and water when the tank was 2/3 full?

Hi

Where is this question from?

Perhaps some info needed for (b) might be missing.

The answer to (a) is 3:4

Divide the tank into 6 units

1/2 filled ----- 3 units
2/3 filled ----- 4 units.

Best wishes