Q&A - PSLE Math

[MathIzzzFun]

oosh:

Hi


Would greatly appreciate some help on this question:

Abel and Ben can build a model aircraft together in 4 days. Ben and Calvin can do the same job together in 1 1/2 times as many days. Abel and Calvin can complete the same job together in twice the number of days Ben and Calvin can do together. If the three boys decide to work together, how long will they take to complete their job?
(Answer: 4 Days)

:thankyou:

Work needed to complete job --> 12 units
A+B --> 4 days --> 3 units/day
B+C --> 1.5 x 4 days = 6 days --> 2 units/day
A+C --> 12 days --> 1 unit/day

Adding...
2 x (A+B+C) --> 6 units/day
(A+B+C) --> 3 units /day
12 units ---> 12/3 = 4 days

A,B and C will take 4 days to complete the job.

cheers.

[oosh]

Michaelia0816:

Hi oosh,


A+B---> 4 days
[B]+C---> 1.5 days
[A]+C---> 1.5 days*2= 3 days

Let see,
A took 1.5 days more than B.
B---> (4-1.5)/2=1.125 days to complete
A---> 1.125+1.5=2.625 days to complete
C--->3-2.625=0.375 days to complete
B+A+C---> 4.125 days
4.125 days~ 4 days ( as it is on the 4 days)

Hi Michaelia, thanks do much for your help but I'm a bit confused coz you mentioned that B + C = 1.5days but the question said that they took 1 1/2 times as many days to complete the job...


Thanks for any assistance.

[oosh]

MathIzzzFun:

oosh:

Hi


Would greatly appreciate some help on this question:

Abel and Ben can build a model aircraft together in 4 days. Ben and Calvin can do the same job together in 1 1/2 times as many days. Abel and Calvin can complete the same job together in twice the number of days Ben and Calvin can do together. If the three boys decide to work together, how long will they take to complete their job?
(Answer: 4 Days)

:thankyou:

Work needed to complete job --> 12 units
A+B --> 4 days --> 3 units/day
B+C --> 1.5 x 4 days = 6 days --> 2 units/day
A+C --> 12 days --> 1 unit/day

Adding...
2 x (A+B+C) --> 6 units/day
(A+B+C) --> 3 units /day
12 units ---> 12/3 = 4 days

A,B and C will take 4 days to complete the job.

cheers.

Hi, thanks so much for your explanation. I can understand this better.

[kwcllf]

Hi, please help with the following question.


John walks to school at an average speed of 4km/h every day. One day, after walking 1km, he realised that his watch was slow. So, he ran at a constant speed to school and reached just on time. Later, he calculated that if he had run at this speed from the start of the journey, he would have reached school 5 minutes earlier. What was his runing speed?

Thanks.

[flying pig]

kwcllf:

Hi, please help with the following question.


John walks to school at an average speed of 4km/h every day. One day, after walking 1km, he realised that his watch was slow. So, he ran at a constant speed to school and reached just on time. Later, he calculated that if he had run at this speed from the start of the journey, he would have reached school 5 minutes earlier. What was his runing speed?

Thanks.

4 km per hour, thus 1 km would take 60/4=15 minutes

since he would have reached school 5 minutes earlier, his running speed would be 15min-5min=10 min taken to run one km.

convert this to km/h and you get 6km/h

[kwcllf]

flying pig:

kwcllf:

Hi, please help with the following question.


John walks to school at an average speed of 4km/h every day. One day, after walking 1km, he realised that his watch was slow. So, he ran at a constant speed to school and reached just on time. Later, he calculated that if he had run at this speed from the start of the journey, he would have reached school 5 minutes earlier. What was his runing speed?

Thanks.

4 km per hour, thus 1 km would take 60/4=15 minutes

since he would have reached school 5 minutes earlier, his running speed would be 15min-5min=10 min taken to run one km.

convert this to km/h and you get 6km/h

Thanks very much for the help :salute:

[kwcllf]

flying pig:

kwcllf:

Hi, please help with the following question.


John walks to school at an average speed of 4km/h every day. One day, after walking 1km, he realised that his watch was slow. So, he ran at a constant speed to school and reached just on time. Later, he calculated that if he had run at this speed from the start of the journey, he would have reached school 5 minutes earlier. What was his runing speed?

Thanks.

4 km per hour, thus 1 km would take 60/4=15 minutes

since he would have reached school 5 minutes earlier, his running speed would be 15min-5min=10 min taken to run one km.

convert this to km/h and you get 6km/h

Thanks very much for the help :salute:

[2DMommy]

MathIzzzFun:

2DMommy:

Please help me with these two questions :


1) Pasqual, Quincy , Robert and Sheridan had a total of 242 muffins. Each of them would have an equal number of muffins if Pasqual bought 10 more muffins, Quincy gave away 21 muffins, Robert increased the number of muffins he had by 2/3 and Sheridan decreased the number of muffins he had by 20%. How many muffins did each of them have ?

2) 0.6 of Luqman's allowance is twice as much as 10% of Zachary's allowance. After Luqman's spends thrice as much as Zachary, Luqman's and Zachary left with $36 and $252 respectively. How much does Zachary and Luqman's each have at first?

Thank you.

Can someone please help me with the above two questions? Thank you !

Both questions could be solved quite easily with MD, I shall use the units approach due to time constraint.

Q1.
In the end, each will have 20u
At first,
P --> 20u -10
Q --> 20u + 21
R --> 12u
S --> 25u
Total --> 77u + 11 = 242
1u --> 33

At first, number of muffins each had :
P --> 650
Q --> 681
R --> 396
S --> 825

cheers.

Hi MathIzzzFun

Can you explain to me how you get the 20u ? Thanks !

[anneshirleygilbert]

Can somebody please help me with this question?


Alan bought 1.5 times as many pencil cases as pens and spent $300 altogether. He spent $60 more on pens than on pencil cases. Given that a pen costs $3.50 more than a pencil case, find the cost of a pencil case.

TIA

[MathIzzzFun]

2DMommy:

MathIzzzFun:

Please help me with these two questions :


1) Pasqual, Quincy , Robert and Sheridan had a total of 242 muffins. Each of them would have an equal number of muffins if Pasqual bought 10 more muffins, Quincy gave away 21 muffins, Robert increased the number of muffins he had by 2/3 and Sheridan decreased the number of muffins he had by 20%. How many muffins did each of them have ?


Thank you.

Can someone please help me with the above two questions? Thank you

Both questions could be solved quite easily with MD, I shall use the units approach due to time constraint.

Q1.
In the end, each will have 20u
At first,
P --> 20u -10
Q --> 20u + 21
R --> 12u
S --> 25u
Total --> 77u + 11 = 242
1u --> 33

At first, number of muffins each had :
P --> 650
Q --> 681
R --> 396
S --> 825

cheers.

Hi MathIzzzFun

Can you explain to me how you get the 20u ? Thanks !

In the end, Robert has 5 blocks (R), and Sheridan has 4 blocks (S). To make them \"equal\", divide into 20 parts ie 4 parts per block for block (R) and 5 parts per block for block (S).

Here's a lengthy with more details than necessary explanation:

http://i46.tinypic.com/2qw3o87.png\">

cheers.