Q&A - PSLE Math

[fantasy1]

Hi MathIzzzFun,


Thank you for yr help

[david59]

MathIzzzFun:

david59:

[quote=\"MathIzzzFun\"]Hi all,

I am inclined to say that the qn is flawed.
If the car's speed is 110km/hr, then in three hours after passing the van and reaching town Q, he would have travelled 330km. However, you rightly calculated that the distance between the point where the car passed the van and town Q is 275km. So, there is a discrepency here.
I suspect the fraction used in the qn is unneccessary. It should have just been \" After travelling for 1/2 hour, the car passed a van travelling at a constant speed of 70km/h in the same direction.
3 hours later, the car reached Town Q but the van was still 65 km away from Town Q\".

Average speed for whole journey does not mean the car travelled at constant speed of 110 km/h throughout.

In this case, for the first 2/7 of the journey, the car's average speed is 220 km/h and for the final 5/7 of the journey, the car's average speed is 91 2/3 km/h

cheers.

[/quote]Looks like the car was racing at extreme speed of 220km/hr in the GrandPrix F1 for half an hour and then suddenly found himself chasing past a van and so slowed down to a crawl at only 91 2/3 km/hr.
This qn is unacceptable for a child to do though technically speaking is not wrong. He would find the first half hr speed too incredible and so doubt his own working.
Good nite!

[tianzhu]

Essential:

Hi Tian Zhu thank you for your help for earlier question. One more question from Nanyang Prelim 2012. Q13. both shops. ABC and XYZ , offered a 15% discount for the same type of mattress. If Mr Muthu were to buy from shop XYZ ,he would have paid $38.25 less than the discounted price in shop ABC. a) What was the discounted price in the shop ABC ?

b) the original price of the mattress in Shop ABC was $1510. what was the minimum percentage discount it must offer so that the discounted price in shop ABC would be lower than the discounted price in Shop XYZ? Give your answer connect to the nearest percent.Thankyou in adv

Hi

15% ------- 38.25

100% ------- 255 (original price in XYZ)

For ABC ------ 255*100/85 ------- 300

a) Difference -------300 – 255 ------- 45

For (b)

Discounted price in ABC -------- 1510*0.85 ------ 1283.50

Discounted price in XYZ -------- 1283.50 – 38.25 ------- 1245.25

1510 – 1425.25 ------- 264.75

264.75/1510*100% ------- 18%

Best wishes

[zanen]

tianzhu:

zanen:

help ls Two cars race around a circular track at constant speeds starting at the same point. If they travel in opposite directions, then they meet every 30 seconds. If they travel in the same direction, then they meet every two minutes. If the track is 1800m long,what is the speed of each car?

Hi

Could you share with us where you take this question from?

Is this a PSLE type of question?

The answers to your question are 22.5m/s and 37.5m/s.

please help me. it was given by the relief teacher from my math teacher. the relief teacher dont know how to teach math ask me to find out by myself//
Best wishes

[zanen]

Tom and Peter stay at Towns A and B respectively which are 500km apart. They arranged to meet up at Town C which is in between Towns A and B, and is x km away from Town A. Tom travelled at an average speed of 90km/h while Peter was 30km/h faster. They set off at the same time and Tom arrived at Town C 40 min earlier than Peter. Form an equation in x and find the time Peter took to reach Town C.

my hw.

[MathIzzzFun]

zanen:

Tom and Peter stay at Towns A and B respectively which are 500km apart. They arranged to meet up at Town C which is in between Towns A and B, and is x km away from Town A. Tom travelled at an average speed of 90km/h while Peter was 30km/h faster. They set off at the same time and Tom arrived at Town C 40 min earlier than Peter. Form an equation in x and find the time Peter took to reach Town C.

my hw.

This is a typical question for Sec 1 students when they learn algebra.

I believe this is your tuition home work. While students can use algebra to solve problems, solving of algebraic equations are not covered in P6 syllabus and not tested in PSLE. For P6, students are required to form equation in x (or any variable the question dictates) but value of x will be provided for the student to work out the answer.
For eg. A pencil cost $2 and a pen cost $2k more. A pencil case cost half as much as the total cost of a pencil and a pen.
a) express the cost of the pencil case in terms of k.
b) if k =0.5, find the cost of a pencil case.

For P6, the question can be solved using speed ratio/distance ratio/time ratio.

Here's a solution using distance ratio:
Tom's speed : Peter's speed = 90:120=3:4
Over the same time, distance travelled by Tom : Peter --> 3u:4u
When Tom reached Town C, Peter is still 40 min away,
total distance travelled = 3u+4u=7u
40 min x 120 km/h = 80 km --> Peter is still 80 km away from C
Total distance between A and B = 500km --> 7u + 80 km
1u --> 60km
Distance of Town C from Town B --> 4u + 80km = 4 x 60 km + 80 km = 320 km
Time taken by Peter to reach Town C = 320/120 h = 2h 40 min

cheers.

[kay22]

http://i47.tinypic.com/347xpn8.jpg\">

[kay22]

Please help...thanks a lot.


http://i50.tinypic.com/2rqkluc.jpg\">

[MathIzzzFun]

kay22:

Please help...thanks a lot.


http://i50.tinypic.com/2rqkluc.jpg\">

unshaded area = 1/2 area of rectangle
shaded area = area of quadrant - 1/2 area of rectangle

perimeter = circumference of quadrant + 2 x radius - 1/2 perimeter of rectangle + radius (diagonal)

cheers.

[kay22]

MathIzzzFun:

kay22:

Please help...thanks a lot.


http://i50.tinypic.com/2rqkluc.jpg\">

unshaded area = 1/2 area of rectangle
shaded area = area of quadrant - 1/2 area of rectangle

perimeter = circumference of quadrant + 2 x radius - 1/2 perimeter of rectangle + radius (diagonal)

cheers.

Thanks for the clarification...We are stuck at \" Radius (diagonal)\". It don't seem to be touching from one end to another.