Q&A - PSLE Math

[paranoid]

MathIzzzFun:

paranoid:

http://i49.tinypic.com/2njc4ko.jpg\">

Killer question from Nanyang Prelim paper
Could someone help me

Thanks so much.

discussed at http://www.kiasuparents.com/kiasu/forum/viewtopic.php?f=69&t=280&start=7950

cheers.

Thanks for your easy-to-understand explanation. It makes the question much easier to solve.

[tianzhu]

match3frog:

Here's another one:

Mr Siew drove from Town X to Town Y at 60km/h. If he increased his speed by 12km/h, he would reach Town Y 1 hour earlier. Find the speed he must travel after the first 120km so that he can reach Town Y 4/5h earlier.

Thank you.

Hi

If your child is familiar with inverse ratio method, here’s the solution.

Speed ratio -------- 60:72 ------- 5:6

Time ratio --------- 6:5

At 60km/h, he took 6h

At 72km/h, he took 5h

Distance between X and Y --------- 360 km

First 120km at 60km/h, remaining 240km.

240/60 ------ 4h

4 – 0.8 ------ 3.2

Speed after first 120km ------- 240/3.2 ------- 75km/h

Best wishes

[MathIzzzFun]

match3frog:

Please help with the following question:


A car was travelling from Town P to Town Q.

After completing 2/7 of the journey in 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.

(a) Find the average speed of the car.

(b) If the van left Town P at 0810, at what time would it arrive at Town Q?

Thank you

5/7of distance PQ --> 3 x 70 + 65 = 275 km
distance PQ --> 275/5 x 7 --> 385 km
total time taken by car --> 3. 5 h
average speed of car --> 385/3. 5 --> 110 km/h

cheers.

[Be a mom]

MathIzzzFun:

Be a mom:

http://i49.tinypic.com/16p0f7.jpg\"> Hi, Pls help on this question!!!!

Remainder --> 11 units
Original amount of money --> 11 units + $1155

Amount left = 11 units - 2 units - $175 = 9 units - $ 175
Amount left = 1/11 original amount --> 1 unit + $105
9 units - $175 = 1 unit + $ 105
1 unit --> $ 35

Amount spent on bag --> $70
original amount of money --> 11 x $35 + $1155 = $1540
... can you work out the solution from here ?
:thankyou: :thankyou: :thankyou:




cheers.

[tech_nomax]

Please help with the following questions:


1) Wendy has big and small chicken and duck eggs in her farm. She has 275 chicken eggs and 225 duck eggs. The ratio of big chicken eggs to small duck eggs is 5:2. The total number of big chicken eggs and big duck eggs is 300. find the total number of small chicken eggs in her farm.

2) Two buses X and Y left ABC interchange at 6.35 a.m. to pick up passengers. They travelled at an uniform speed in opposite directions round a 55 km circular route. Bus X took 50 minutes to complete each round. After every 30 minutes, the two buses would meet. At what time would the two buses meet at the interchange again?

Thank you.

[match3frog]

Thanks so much for your prompt and clear solutions, tianzhu and mathizzzfun!


:thankyou:

[charsen]

tech_nomax:

Please help with the following questions:


1) Wendy has big and small chicken and duck eggs in her farm. She has 275 chicken eggs and 225 duck eggs. The ratio of big chicken eggs to small duck eggs is 5:2. The total number of big chicken eggs and big duck eggs is 300. find the total number of small chicken eggs in her farm.

2) Two buses X and Y left ABC interchange at 6.35 a.m. to pick up passengers. They travelled at an uniform speed in opposite directions round a 55 km circular route. Bus X took 50 minutes to complete each round. After every 30 minutes, the two buses would meet. At what time would the two buses meet at the interchange again?

Thank you.

Hi
Q1.
Chicken Ducks
Big 5u P 300
small S 2U 200
275 225 500

225-2u=300-5U
3U=75
1U=75/3=25
275-(25x5)=150(ANS)

[jewelbox]

MathIzzzFun, thanks for the soln on vol of water in tank with tap A and B. I dont understand why must ‘assuming tap A fill tank in last 3 min’ and the steps after it.


Why cant i do :
Since it takes 6min to fill 0.9cm, it takes 500min to fill 75cm. Thus ans is 500min.
Thanks.

[zanen]

someone pls help Mr Tan drives from Town A to Town B, a distance of 720 km,at a constant speed. When he returns from Town B to Town A, he saves an hour of travel time by increasing his average speed by 10 km/h. Find the total time taken for the whole journey (to and fro).

[zanen]

pls help wif this too my teacher mc for two weeks There were some sweets in the bag,A,B,C,D.Marc ate some sweets from bag A and added some more sweets to bag B.Je then took 1/6 of the sweets from bag C and put them in bag D.the number of sweets in bag A decreased and the numberof sweets in bag B increased by 60%.There was an equal number of sweets in the end.If there were 192 sweets in bag D at first,how many sweets were there in bags A,B,C altogether at first?