Q&A - PSLE Math

[tianzhu]

Winx5015:

Using restating problem
Q2). 3 similar tables and 4 similar chairs cost $240. 2 such tables and 3 similar racks cost $115. 1 such chair and 2 such racks cost $95. How much do 2 such tables and 1 such chair cost altogether?

Hi

3T + 4C ------ 240
2T + 3R ------ 115
1C + 2R ------ 95

5T + 5C + 5R ------- 450 (240+115+95)

1T + 1C + 1R ------- 90
(x2)
2T + 2C + 2R ------- 180

1C + 2R ------ 95

Therefore, 2T + 1C ------ 180 – 95 ------85

Best wishes

[peggy]

Please help with this question. Thanks in advance.


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?

[tianzhu]

peggy:

Please help with this question. Thanks in advance.


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?

Hi

There are a few ways to solve this question.

One way is to use inverse proportion.

Speed is inversely proportional to time (distance remains constant).When speed is higher, time taken is shorter.

Speed ----- 2:3 (10:15)
Time ------- 3:2

1 unit ------ 2h (1pm and 3pm)

2 units ------ 4h
Distance ------- 15*4 ------- 60km

Alternatively
3 units ------ 6h
Distance ------ 10*6 ------ 60km

If he wants to reach the church@2pm

Time taken ------5h

60/5 ------ 12km/h

Best wishes

[peggy]

Tianzhu,


Thank you so much for your quick reply.

All the best!

Peggy

[JGMum]

jarenchuatw:

Yup, 100% correct. But had problem explaining to my son, he could not comprehend why I need to add 8 secs and not 12 seconds. Whew, it took a while before he got the picture. Tks!

That's great, thanks for the feedback!

[Winx5015]

Hi tianzhu,


thanks for your solution.

Good nite

[Michaelia0816]

Do try to find the answer as it was a great example of Math PSLE. I would tell the correct again later in a while. DO post your answer!

The Lim family were great mathemacticians. When a reporter wanted to interview them, she asked for everyone's ages! The family replied to her, \" Our family of 2 adults and 3 children are a total of 100 years old together. The sum of father and his son ages was 51 years old. The mother ages was 3 years younger than the father while the twins daughter were each 5 years younger than her brother.\" So what were their ages ? (Hint: Draw model)
:xedfingers:

[tianzhu]

Michaelia0816:

Do try to find the answer as it was a great example of Math PSLE. I would tell the correct again later in a while. DO post your answer!

The Lim family were great mathemacticians. When a reporter wanted to interview them, she asked for everyone's ages! The family replied to her, \" Our family of 2 adults and 3 children are a total of 100 years old together. The sum of father and his son ages was 51 years old. The mother ages was 3 years younger than the father while the twins daughter were each 5 years younger than her brother.\" So what were their ages ? (Hint: Draw model)
:xedfingers:

Hi

If I remember correctly, a similar question has been discussed before.

Daughter ------ 6
Son ------ 11
Father ------- 40
Mother ------ 37

Best wishes

[tianzhu]

Hi


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.

http://farm8.staticflickr.com/7140/7010307049_02abdcfae5_z.jpg\">

[YumYum]

Hi, need help with this Qn:


Rachel and Nicole set off the park and travelled towards their school at the same time. At 10 am, Rachel was 600m ahead of Nicole.

Nicole caught up with Rachel at 10.30am.

Given that rachel travelled at an average speed of 60 m/min , find nicole’s average speed.

Thanks