Free Primary School Maths Help - You Post I Solve!

[fridayeducation]

suiyuan:

3)Town A and Town B were 600 km apart. At 10.45 am, a lorry travelling at a uniform speed left Town A for Town B. At the same time, a taxi set off from Town B to Town A at a uniform speed which was 12 km/h faster than that of the lorry's. The two vehicles met at 3.45 pm. Find the speed of the taxi.

The concept of this concept is the same as that of question 1. Distance and time is provided in this question and then one vehicle is faster than another. In this question, time is provided when they state time vehicles set off and time they met. It is all the same.

As long as DISTANCE & TIME are the given AND they are comparing 2 vehicle's speed (coming/going in opposite direction), this is how you should solve, remember that TOTAL SPEED in this case includes speed for both lorry and taxi.

Using Formula, Distance = Speed x Time

600km = 5h (Total Speed)
120km/h = Total Speed
\t= Lorry's Speed + Taxi's Speed
\t= Lorry's Speed + Lorry's Speed + 12km/h
108km/h = Lorry's Speed + Lorry's Speed
54km/h \t= Lorry's Speed

Taxi's Speed - 54km/h + 12km/h = 66km/h

(To check, always check)

They both travelled 5hours and they met, so the distance they've travelled must add up to distance given, 600km

Lorry's Distance - 5h x 54km/h = 270km
Taxi's Distance - 5h x 66km/h = 330km
Total Distance - 270km + 330km = 600km

[suiyuan]

fridayeducation:

kiasiparent:

When Mrs Lee was 40 years old, her son was twice her daughter's age. Mrs Lee will be twice her son's age when her daughter is 28 years old. How old will Mrs Lee be when her daughter is 20 years old?

Mrs Lee will be 56 years old when her daughter is 20 years old. I've just got back and had done this by logic and guess & check. perhaps you'll like to let me know what level is your child or is this question intended for so i can prepare a solution catered to the understanding of the level? Thanks.

Hi
This is a question from P6.

[corneyAmber]

kiasiparent:

When Mrs Lee was 40 years old, her son was twice her daughter's age. Mrs Lee will be twice her son's age when her daughter is 28 years old. How old will Mrs Lee be when her daughter is 20 years old?

You can find the answer here:

http://madabtmath.wordpress.com/2008/10/23/p6-math-momdsdd-age/

[suiyuan]

Hi

fridayeducation

Thank you for your answers.

[acforfamily]

suiyuan:

2)Mr Lee and Mr Tan both drove from Town X to Town Y. Mr Lee started his journey at 10.00 am travelling at an average speed of 75 km/h. Sometime later, Mr Tan started his journey. At 12.00 noon, Mr Tan overtook Mr Lee. When Mr Tan reached Town Y at 2.00 pm, Mr Lee was still 50 km from Town Y. Find (a) Mr Tan's average speed (b) The time at which Mr Tan started his journey

Hi, can it be done this way without finding the total distance.

(a)\tMr Tan’s average speed

Using Formula, Distance = Speed x Time
Distance travelled by Lee in the same time from 12 noon to 2 pm = 75km/h *2h = 150 km
Since Lee is 50 km away from town Y, Tan would have travelled 150km+50km = 200km in the same time

Using Formula, Speed = distance / Time
Tan’s speed = 200 km / 2 h = 100 km/h

(b)\tTime that Tan started
Distance that Lee has travelled before Tan overtook him = 75km/h*2h = 150 km
Using Formula, time = Distance / Speed

Time taken for Tan to overtake him = 150 km / 100 km/h = 1.5 hours
Which means 12 noon less 1.5 hours, that would be 10.30 am that he started

[fridayeducation]

acforfamily:

Hi, can it be done this way without finding the total distance.

(a)\tMr Tan’s average speed

Using Formula, Distance = Speed x Time
Distance travelled by Lee in the same time from 12 noon to 2 pm = 75km/h *2h = 150 km
Since Lee is 50 km away from town Y, Tan would have travelled 150km+50km = 200km in the same time

Using Formula, Speed = distance / Time
Tan’s speed = 200 km / 2 h = 100 km/h

(b)\tTime that Tan started
Distance that Lee has travelled before Tan overtook him = 75km/h*2h = 150 km
Using Formula, time = Distance / Speed

Time taken for Tan to overtake him = 150 km / 100 km/h = 1.5 hours
Which means 12 noon less 1.5 hours, that would be 10.30 am that he started

Yupp! Your answer is shorter and more direct than me. Thanks for sharing!

[suiyuan]

Thank you for your help.


P6 Maths

Q1) A van left Metropolis Town and travelled towards Gotham Town at an average speed of 80 km/h. An hour later, a car left Metropolis Town and travelled towards Gotham Town at an average speed of 100 km/h. The car passed Keystone Town, which was halfway between Metropolis Town and Gotham Town, 30 minutes earlier than the van. The car reached Gotham Town at 10 pm. At what time did the van leave Metropolis Town for Gotham Town?

Q2) At 9.00 am, Mr Lee's car passed a certain point X, travelling at an average speed of 60 km/h. At 10.30 am, Mr Chua's car started off from point X at an average speed of 80 km/h in pursuit of Mr Lim's car. (a) At what time did Mr Chua's car overtake Mr Lim's car (b) How far was Mr Chua's car from point X when it overtook Mr Lim's car?

Q3) A car and a van were travelling from Town P to Town Q which were 480 km apart. The van left Town P at 8.15 am and drove towards Town Q at an average speed of 64 km/h. The car set off 1 hour later than the van but it arrived at Town Q 15 minutes earlier. (a) At what time did the car arrive at Town Q? (b) How much faster was the car travelling than the van per hour?

[Vanilla Cake]

fridayeducation:

I will be providing you help with questions that you have doubts on.


You may post the questions here/PM me or email me and I will try my best to solve it at soonest and post the question/answer here so other parents who have doubts on the same type of questions may help their kids too

TIA for helping to solve these P6 questions.

Q1
The distance between A and B is 7 km. At the beginning, both Gregory and Catherine are at A. Gregory walked from A to B at a constant speed. After Gregory had walked for 1 km, Catherine discovered that he had left his belongings at A. She immediately ran after him at a constant speed of 4 km/h. After handing over the belongings to Gregory, she turned back and started running towards A at the same speed. Given that both Catherine and Gregory reached A and B respectively at the same time, what was Gregory’s speed?

Q2
Paul and James went out for a cycle and were 16 km from home when Paul ran into a tree damaging his bicycle beyond repair. They decide to return home and that Paul will start on foot and James will start on his bicycle. After some time, James will leave his bicycle beside the road and continue on foot, so that when Paul reaches the bicycle he can mount it and cycle the rest of the distance. Paul walks at 4 km per hour and cycles at 10 km per hour, while James walks at 5 km per hour and cycles at 12 km per hour. For what length of time should James ride the bicycle, if they are both to arrive home at the same time?

[kiasiparent]

1) 3km/h. Just draw a simple diagram


2) A to B: Paul on foot at 4 km/h
James on bicycle at 12 km/h
B to Paul on bicycle at 10 km/h
James on at foot 5 km/h
∴ Total time for Paul = Total time for James
x/4+(16-x)/10 = x/12 +(16-x)/5
x = 6 km

[Jolyn]

I have a Question for P2 which need help on the explaination on the answer as below:


Q1
Ravi and Timothy have a total of 468 Stamps. They have the same number of stamps. How may stamps must Timothy give to Ravi so that Ravi can have 50 more stamps than Timothy?

Thanks for your advise.