Q&A - P3 Math

[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!

[peterch]

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!

1st:
TOM XXXXX XXXXX XXXXXX
LING XXXXX XXXXX ( 160 ) This is the difference

After Tom gave away 230:
TOM XXXXX ( 70 ) ( 160 ) Tom gave away 230 ( 160 + 70)
LING XXXXX XXXXX

XXXXX= 70

So at first TOM had 70 + 70 + 160 = 300 Marbles

[just888]

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.

Even me also made mistake..let alone a young kid. :stupid:

[Atan]

peterch:

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!

1st:
TOM XXXXX XXXXX XXXXXX
LING XXXXX XXXXX ( 160 ) This is the difference

After Tom gave away 230:
TOM XXXXX ( 70 ) ( 160 ) Tom gave away 230 ( 160 + 70)
LING XXXXX XXXXX

XXXXX= 70

So at first TOM had 70 + 70 + 160 = 300 Marbles

Tks peterch, but we still don't understand why XXXXX=70, pls assist to explain further.

[Just4Good]

Atan:

peterch:

[quote=\"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!

1st:
TOM XXXXX XXXXX XXXXXX
LING XXXXX XXXXX ( 160 ) This is the difference

After Tom gave away 230:
TOM XXXXX ( 70 ) ( 160 ) Tom gave away 230 ( 160 + 70)
LING XXXXX XXXXX

XXXXX= 70

So at first TOM had 70 + 70 + 160 = 300 Marbles

Tks peterch, but we still don't understand why XXXXX=70, pls assist to explain further.[/quote] ________________
Tom l________________l
____________
Ling l___________ l 160

Tom gave away 230 marbles, and Ling had twice as many marbles as him.
_______ _____________________
Tom l_______l____ GAVE AWAY 230__l
______________
Ling l______________l 160

If Tom gave away 160 marbles ONLY, he would have as many marbles as Ling but he gave away 70 more. If you see properly, 70 is HALF of Ling's model. Since it's like this, Tom has 70 marbles NOW. You add the 230 he gave away, you get 300.

230-160=70
70+230=300.

Ans: 300 marbles.

[Atan]

Tks! All4Good and peterch. Earlier on, I thought that Tom gave away 230 marbles to Ling, so couldn't understand :oops: . So Sotong.

[just888]

Hi, I got problem trying to work this out:


Question:
Mrs A wanted to buy 24 cans of tuna, but she was short of $2. She bought 21 cans of tuna and had $2 left. How much money did she have at first?

MTIA.

[Suz855]

24-21=3

3 cans-->$4
21/3 = 7
7*4=28
28+2=30

She has $30 at first.

[just888]

Suz855:

24-21=3

3 cans-->$4
21/3 = 7
7*4=28
28+2=30

She has $30 at first.

Thanks alot.