Q&A - PSLE Math

[whitety]

MathIzzzFun:

whitety:

Hi, need help on these 2 qns.


1) George and Hamid drove at constant speeds from City A to City B. They started their journey at the same time. When George completed 3/4 of the journey, Hamid was 18km behind George. George reached City B 20min before Hamid. Find Hamid's speed in km/h.

2) in a bag, the ratio of the number of $2 notes to the number of $10 notes was 2:5. Ten $10 notes were removed from the bag to exchange for $2 notes which were then put back into the bag. The total value of money in the bag was unchanged after the exchange. The ratio of the number of $2 notes to the number of $10 notes then became 11:5. What was the difference between the value of the $10 notes and $2 notes after the exchange?

Thanks!

1) George completed 3/4 of journey, Hamid 18km behind
So, when George completed the journey (4/4), Hamid will be 24km behind
Hamid's speed = 24km/20 x 60 km/h = 72 km/h

2) 10 x $10 = 50 x $2
At first, number of $2 notes: $10 notes --> 2u : 5u
In the end, number of $2 notes: $10 notes --> 2u+50 : 5u-10 = 11 : 5

cross multiply/equalize:
10u + 250 = 55u - 110
1u --> 8 .. can you continue from here ?

difference in value = $168 ($10 --> $300, $2--> $132)

cheers.

:boogie: :thankyou: :boogie:

[MathIzzzFun]

2632parent:

Good morning, really need help on this simple question? I just cannot get the answer -25m.


1) Sam and Jedi took part in a 100m race. When Sam had run 80m, Jedi only managed to run 60m. How far was Jedi from the finishing line when Sam just dashed through it?

Many thanks

Distance run by
Sam : Jedi --> 80 : 60 = 4:3 = 100: 75
100m - 75 m = 25m --> Jedi would be 25m behind

cheers.

[MathIzzzFun]

mom-of-2:

Hi, would appreciate help with this sum :


Raju took 8 hours to drive from town X to town Y. Robert who started at the same time as Raju took 6 hours to drive from town Y RI town X. When they meet each other , they were 56 km away from the midpoint of town X and town Y. What was Raju's average speed ?

Thank you in advance !

Please refer to similar question that was discussed at
http://www.kiasuparents.com/kiasu/forum/viewtopic.php?f=69&t=280&start=7600

cheers.

[Chan09]

Need help on these; thank you


1) team A and team B sent pupils in groups of 10, for a ball game. If the 2 teams used mini vans that have a seating capacity of 14 passengers, they will need 72 vans. If they use mini vans that have a seating capacity of 19, team B will need 7 more vans than team A. If the 2 teams do not share a van and each van is pack to a max of 19 for team B, how many more pupils are there in team B than team A?
Ans: 140

2) There are 98 teachers and each female teacher has 8 notepads and each male teacher has 3 notepads given to them. The male teachers received 355 notepads less than the female teachers. How many female teachers are there?
Ans: 59, for this question I applied the excess and shortage concept though I understand that this is incorrect as it is suppose to make a supposition. Plse help.

[MathIzzzFun]

Treelodge:

Can some please help to do this Q? :imdrowning:

:thankyou: :thankyou:

Car A and Car B left Town Y at the same time, heading in the opposite direction. Car A headed for Town Z while CAr B left for Town X. The speed of Car B was 20km/h faster than Car A. After 1/2 h, Car A had completed 2/3 of its journey while Car B had completed 1/2 of its journey. The two cars were also 110km apart.
a) Calculate the speed of Car A
b) How far was Car B from Town X when Car A reached its destination?
:?: :thankyou:

after 1/2h, 20km x 1/2 =10 km --> Car B would have travelled 10 km more than Car A.
Distance travelled by A --> 1 unit
Distance travelled by B --> 1 unit + 10 (1/2 journey)
Total 2 units + 10 --> 110
1 unit --> 50 km
A's speed = 50 km ÷ 1/2 = 100 km/h

Fraction of journey travelled by A : B
= 2/3 : 1/2
= 1 : 3/4
When A reached its destination, B would have travelled 3/4 of its journey ie it will still have 1/4 of the journey to travel
1/2 journey --> 1 unit + 10 = 60 km
1/4 journey --> 30 km

Car B will be 30 km from X.

cheers.

[mumworks]

Thanks Speedmaths.com and MathIzzzFun for helping to answer my earlier questions.


Can anyone help on this Qs ?

1/2 of a rectangle overlaps with 1/3 of a circle. What fraction of the figure is overlapped ?

Thank you very much.

[fightingmom]

Hi,


Please help with the following question :

At 7am, Car A left Town X for Town Y while Car B left Town Y for Town X. At 3pm, the two cars passed each other. 5 hours later, Car A reached Town Y but Car B was still 150km away from Town X. Find the distance between Town X and Town Y.

TIA!

[MathIzzzFun]

mumworks:

Thanks Speedmaths.com and MathIzzzFun for helping to answer my earlier questions.


Can anyone help on this Qs ?

1/2 of a rectangle overlaps with 1/3 of a circle. What fraction of the figure is overlapped ?

Thank you very much.

1/2 rectangle = 1/3 circle
rectangle --> 2 units
circle --> 3 units
overlapped --> 1 unit

can you continue from here ?

cheers.

[jarenchuatw]

Got another question to to ask - see attached, but ignore the writing in blue (coz I m not sure whether it is correct or not)

[MathIzzzFun]

fightingmom:

Hi,


Please help with the following question :

At 7am, Car A left Town X for Town Y while Car B left Town Y for Town X. At 3pm, the two cars passed each other. 5 hours later, Car A reached Town Y but Car B was still 150km away from Town X. Find the distance between Town X and Town Y.

TIA!

concept of combined speed

When Car A and Car B meet, the total distance covered is XY and the total time taken is 8 hours (7am to 3pm).

5 hours after passing each other, remaining distance to be covered = 150 km

Both cars took 3 hours (8-5) to cover a total distance of 150 km,
combined speed --> 150 km/3h = 50km/h (quite a slow speed considering that this is a combined speed)
Total distance between XY = 50 km/h x 8h = 400 km

cheers.