Q&A - P3 Math

[atutor2001]

ksi:

atutor2001:

[quote=\"Just4Good\"]The following is a P3 Standard Question:


Owen has a total of 20 oranges and pears. If he exchanges every pear for 2 oranges, he will have 24 oranges. How many oranges does he have?
(1) 8
(2) 10
(3) 12
(4) 44
(5) None of the above.

Pls advice which is the best answer. Thanks.

Answer should be (1) i.e. 8 oranges. It is a test on England or is this madematics.

Should it be \"How many oranges does he have at first?\"[/quote]They like to use the word \"if\" to create a false sense that there was a \"change\". However, \"if\" implies \"has not happened (yet)\". As such, there is no change to the number of oranges or pears.

[24hr-mum]

i thot the answer is like this:

if he exchanges 1 pear (ie give away 1 pear), he will have 2 oranges.
in order to have 24 oranges, he must give away 24/2=12 pears.
if he has 12 pears, then 20-12=8, ie he shd hv 8 oranges (at first)

[Just4Good]

I admit that the question is quite unclear, even though I did NOT miss out a single word. The answer is : Option 1 (8).

[Just4Good]

The following statement ‘he will have 24 oranges’ can mean including the original 8 apples or excluding.

[jedamum]

Just4Good:

I admit that the question is quite unclear, even though I did NOT miss out a single word. The answer is : Option 1 (8).

this type of question penalises kids that think too much.

[Just4Good]

jedamum:

Just4Good:

I admit that the question is quite unclear, even though I did NOT miss out a single word. The answer is : Option 1 (8).

this type of question penalises kids that think too much.

I must have did the worst thing when answering that question. There was no option (5) so I added it in and put '5' in the bracket. My parents call that 'hao lian' and 'shd just guess'. Not surprisingly, I got it wrong.

[24hr-mum]

if we parents were to retake psle now, we probably will fail miserably…

[corneyAmber]

jedamum:

Just4Good:

I admit that the question is quite unclear, even though I did NOT miss out a single word. The answer is : Option 1 (8).

this type of question penalises kids that think too much.

Actually this question can go be elimination because answers (2), (3) and (4) are not possible.

[atutor2001]

Actually that was a very good question for learning "Math keywords". The question highlighted the importance of 2 keywords : "IF" and "TOTAL".


"IF" means it didn’t happen at all. So there is no "Before" and "After".]

No "total" means the number given may not be the total so don’t assume. (there are exceptions)

One of my kids’ teacher reiterated these keywords to them since P3 and it has proven to be very useful in later years.

PS
Another important word is "each"

John and Mary has a total of 20 marbles. (total is 20)
John and Mary has 20 marbles. (although there is no "total" 20 is the total)
John and Mary has 20 marbles each. (each one has 20 marbles)

[Atan]

Pls help to solve this Question:


Tom had 160 more marbles than Ling at first. After Tom gave away 230 marbles, Ling had twice as many marbles as Tom. How many marbles did Tom have at first?

Thanks very much in advance!