Q&A - PSLE Math

[dazzlego]

superhappy:

weatherbee:

Need to draw the model but I don't know how to draw here to show you. Basically, make the numerator the same. So 1/4 = 3/12. Albert has 5 units in total and Bernard has 12 units. Their difference is 12-5=7. Since 7 is 1/2 of what Caleb has, therefore Caleb has 14 units. So,


14 units ---> $210
1 unit ---> $210/14 = $15
Total: 31 units
31 units ---> $15 X 31 = $465

Oh.. Thanks!
I get it now after drawing the model.

However it would not be a good choice to draw model every time you solve this. The figure given in the question might not always be convenient for you to draw the model.
Therefore in future, just remember that the key point to answer this question is to make the numerator to be the same units.

Cheers :celebrate:

[Bookwrappers]

Hi all, i hv a question to ask.


Danny needs to send a parcel which requires postage of $3.35 and $2.35 respectively.
He has 10 stamps each of denomination 26c, 32c, 50c and 80c. Find out the best combination of stamps that he could use so that he would overpay the least.

Ans:
For $3.35 parcel
26c - _______
32c - _______
50c - _______
80c - _______

For $2.35 parcel
26c - _______
32c - _______
50c - _______
80c - _______

Is this guess and check? Any other methods other than guess and check?

[MathIzzzFun]

Bookwrappers:

Hi all, i hv a question to ask.


Danny needs to send a parcel which requires postage of $3.35 and $2.35 respectively.
He has 10 stamps each of denomination 26c, 32c, 50c and 80c. Find out the best combination of stamps that he could use so that he would overpay the least.

Ans:
For $3.35 parcel
26c - _______
32c - _______
50c - _______
80c - _______

For $2.35 parcel
26c - _______
32c - _______
50c - _______
80c - _______

Is this guess and check? Any other methods other than guess and check?

There are multiple answers for this question.

note that all the stamp denomination is even, so the least amount to overpay is 0.01 ie total to $3.36 and $2.36

There are many combinations to get a \"6\" --> 6 x 26 or 3 x 32 or 1 x 26 or a combination of multiples of 32 and multiples of 26 (eg 2 x32 + 2 x 26)

One possible solution
For $3.35 parcel, $3.36 --> 3 x $0.32 + 3 x $0.80
For $2.35 parcel, $2.36 --> 6 x $0.26 + 1 x $0.80

If required least number of stamps:
For $ 3.35 parcel (6 stamps)
$3.36 --> 3 x $0.80+ 3 x $0.32 or (2 x $0.80 + 3 x $0.50 + 1 x $0.26)

For $ 2.35 parcel (4 stamps)
$2.36 --> 2 x $0.80 + 1 x $ 0.50 + 1 x $0.26


cheers.

[Robertpattinsonidle]

MathIzzzFun:

Bookwrappers:

Hi all, i hv a question to ask.


Danny needs to send a parcel which requires postage of $3.35 and $2.35 respectively.
He has 10 stamps each of denomination 26c, 32c, 50c and 80c. Find out the best combination of stamps that he could use so that he would overpay the least.

Ans:
For $3.35 parcel
26c - _______
32c - _______
50c - _______
80c - _______

For $2.35 parcel
26c - _______
32c - _______
50c - _______
80c - _______

Is this guess and check? Any other methods other than guess and check?

There are multiple answers for this question.

note that all the stamp denomination is even, so the least amount to overpay is 0.01 ie total to $3.36 and $2.36

There are many combinations to get a \"6\" --> 6 x 26 or 3 x 32 or 1 x 26 or a combination of multiples of 32 and multiples of 26 (eg 2 x32 + 2 x 26)

One possible solution
For $3.35 parcel, $3.36 --> 3 x $0.32 + 3 x $0.80
For $2.35 parcel, $2.36 --> 6 x $0.26 + 1 x $0.80

If required least number of stamps:
For $ 3.35 parcel (6 stamps)
$3.36 --> 3 x $0.80+ 3 x $0.32 or (2 x $0.80 + 3 x $0.50 + 1 x $0.26)

For $ 2.35 parcel (4 stamps)
$2.36 --> 2 x $0.80 + 1 x $ 0.50 + 1 x $0.26


cheers.

good answer...but is there a shorter answer...like using LCM?

[vivopenguin]

I am a Primary 5 but I do not know about algebra. I have a question and I hope you can solve it and explain how to do it.

Simply 8y-6y/2+3.

[dazzlego]

vivopenguin:

I am a Primary 5 but I do not know about algebra. I have a question and I hope you can solve it and explain how to do it.

Simply 8y-6y/2+3.

Hi vivopenguin,

I think u have implicitly learned algebra before.
U can assume the y in the algebra here as a unit
8units - 6 units / 2 + 3
Can you do this? Of course you can!

Applying the order of operation, do the division first
8 units - 3 units + 3 = 5 units + 3

In algebra,
8y - 3y + 3 = 5y + 3

Isn't it the same?

So the answer for the question given is 5y+3

Hope it helps :celebrate:

[jonaandr]

Please help to solve this problem sum, thanks!


Jim bought some chocolates and gave half of it to Ken. Ken bought some sweets and gave half of it to Jim. Jim ate 12 sweets and Ken ate 18 chocolates. The ratio of Jim’s sweets to chocolates became 1:7 and the ratio of Ken’s sweets to chocolates became 1:4. How many sweets did Ken buy?

[MathIzzzFun]

jonaandr:

Please help to solve this problem sum, thanks!


Jim bought some chocolates and gave half of it to Ken. Ken bought some sweets and gave half of it to Jim. Jim ate 12 sweets and Ken ate 18 chocolates. The ratio of Jim's sweets to chocolates became 1:7 and the ratio of Ken's sweets to chocolates became 1:4. How many sweets did Ken buy?

this was discussed before and there are various ways to solve - using model, Units/Parts, algebra... you can search for the solutions using keywords eg. \"Jim bought some chocolates\"

http://i49.tinypic.com/esqept.png\">

cheers.

[Verysuperkiasu]

I have a question abt speed.


If the question states the motorist moving from one point to another at a certain speed, then rest for sometime, for example 40min. Then he continue journey for 2nd half.

If the question asks the average speed for 2nd half, do we take into account the 40 min? What if the question asks for the average speed for entire journey , then do we take time taken as inclusive of the 40min rest time?

[elkniwt]

Verysuperkiasu:

I have a question abt speed.


If the question states the motorist moving from one point to another at a certain speed, then rest for sometime, for example 40min. Then he continue journey for 2nd half.

If the question asks the average speed for 2nd half, do we take into account the 40 min? What if the question asks for the average speed for entire journey , then do we take time taken as inclusive of the 40min rest time?

average speed for 2nd half -> don't include 40min rest time
average speed for entire journey -> have to include 40min rest time