Q&A - P3 Math

[peapot]

Hi what method to use for this q?


Darren has some 10cent coins, 20cent coins and 50 cent coins in his pocket that add up to $2. He has exactly 9 coins. How many 20 cent coins does he have?

I found 2 answers. either 3 twenty cent coins or 7 twenty cent coin. Which should be correct?

[peapot]

if i use guess and check method it will be 7 twenty cent coin.

[peapot]

sorry one more q which I cannot understand why the teacher mark it wrong.


In a quiz, a pupil is awarded 2 sweets for every 7 correct answers. How many sweets will he receive for 56 correct answers? My girl’s answer is 16. Why is it wrong?

[Pris.011283tang]

peapot:

sorry one more q which I cannot understand why the teacher mark it wrong.


In a quiz, a pupil is awarded 2 sweets for every 7 correct answers. How many sweets will he receive for 56 correct answers? My girl's answer is 16. Why is it wrong?

peapot i also arrive at the same answer did u check with the teacher why isit qrong?

2sweets-7 correct answer
4sweets-14
6sweets-21
8sweets-28
10sweets-35
12sweets-42
14sweets-48
16sweets-56

[HAPPYH]

peapot:

sorry one more q which I cannot understand why the teacher mark it wrong.


In a quiz, a pupil is awarded 2 sweets for every 7 correct answers. How many sweets will he receive for 56 correct answers? My girl's answer is 16. Why is it wrong?

Yes, your DD's answer is correct.

[HAPPYH]

peapot:

Hi what method to use for this q?


Darren has some 10cent coins, 20cent coins and 50 cent coins in his pocket that add up to $2. He has exactly 9 coins. How many 20 cent coins does he have?

I found 2 answers. either 3 twenty cent coins or 7 twenty cent coin. Which should be correct?

Other than guess and check, is there any other way to solve this problem (3 variables)? For example, there are few steps we can follow if there is 2 variables (cows and ducks or cars and bicycles) to arrive at the answer. Similarly, is there anything that we can follow to do this sum? My DD can do guess and check only if it is small numbers. Worried what if the numbers get bigger and bigger. Thank you in advance.

[Divha]

Hi,


Could anybody help to solve this problem using model ?

Gina had $75 and Wendy had $125.
After Wendy gave Gina some money, she had $40 less than Gina. How much money did Wendy give to Gina ?

Thanks a lot.

[VbusyMum]

Divha:

Hi,


Could anybody help to solve this problem using model ?

Gina had $75 and Wendy had $125.
After Wendy gave Gina some money, she had $40 less than Gina. How much money did Wendy give to Gina ?

Thanks a lot.

The answer is $5. I don't know how to draw model using my iPad. Attempted below. Hope it is clear. \"X\" is the part that is transfer so u need to find the remaining 2 units (marked as ?) after putting aside the 40 which is extras from the original 50. The difference divide by the 2 units.

Do ignore the EXT as I have to out it there to make sure the 50 is mark in the correct position of the model.

Workings:
50-40=10
10/2=5

Ext |_____________|<----50------->

W. |_____75______|_?_|_40_|_X_|

G. |_____75______|_?_|

[php]

Divha:

Hi,


Could anybody help to solve this problem using model ?

Gina had $75 and Wendy had $125.
After Wendy gave Gina some money, she had $40 less than Gina. How much money did Wendy give to Gina ?

Thanks a lot.

Using Total Unchanged Concept to solve the problem

After Model :-

Wendy <---------------->
1 unit
Gina <-------------------------------->
1 unit + $40

2 units + $40 --> $200
2 units --> $160
1 unit --> $80

Before : Wendy --> $125
After : Wendy -- > $80

Ans : $125 - $80 = $45....

[Lynn2010]

Ans is 45