Q&A - P3 Math

[tianzhu]

fohope:

Hi,

Pls help me to solve these problems and thanks in advance to everyone.
1) 21 handshakes were exchanged at a party. If each person only shook hand with another person once, how many people were there at the party?

Hi

This question is pretty similar to yours.Try to understand the logic behind the solution and apply it to your question.

The answer to your question is 7.

Best wishes.

http://farm6.staticflickr.com/5307/5668798707_dd4d6f1925_z.jpg\">

[Cher2101]

Dear parent is there a method to answer the below question.


A) there are 16 ducks and cows on a farm altogether. The animals have 60 legs In all. How many ducks and how many cows are there on the farm?

[php]

Cher2101:

Dear parent is there a method to answer the below question.


A) there are 16 ducks and cows on a farm altogether. The animals have 60 legs In all. How many ducks and how many cows are there on the farm?

Using Chicken-Rabbit Concept,

Assume all are ducks

16 x 2 = 32 legs

60 - 32 = 28

Diff in legs --> 4 - 2 = 2

No of cows --> 28 div 2 = 14
No of ducks --> 16 - 14 = 2

For checking,

(14 x 4) + (2 x 2) = 56 + 4 = 60

[HAPPYH]

php:

Cher2101:

Dear parent is there a method to answer the below question.


A) there are 16 ducks and cows on a farm altogether. The animals have 60 legs In all. How many ducks and how many cows are there on the farm?

Using Chicken-Rabbit Concept,

Assume all are ducks

16 x 2 = 32 legs

60 - 32 = 28

Diff in legs --> 4 - 2 = 2

No of cows --> 28 div 2 = 14
No of ducks --> 16 - 14 = 2

For checking,

(14 x 4) + (2 x 2) = 56 + 4 = 60

I am aware this method for 2 variables. Can we apply this for 3 variables, say cows, ducks and one more animal say insect or 10-cent, 20-cent and 50-cent coins? Thanks in advance.

[Michaelia0816]

Not possible, to use three, but after comparing two and found one of it, use it for another to compare.

[HAPPYH]

Michaelia0816:

Not possible, to use three, but after comparing two and found one of it, use it for another to compare.

Could you please help me solve the following problem using the above method? Thank you in advance.

Si Rong had 8 50 cent-coins, 20 cent coins and 10 cent coins that add upto $2. How many 50 cent coins does she have?

[peapot]

If three items then need to use guess and check. This was what I was told by the school teacher.

[corneyAmber]

HAPPYH:

Michaelia0816:

Not possible, to use three, but after comparing two and found one of it, use it for another to compare.

Could you please help me solve the following problem using the above method? Thank you in advance.

Si Rong had 8 50 cent-coins, 20 cent coins and 10 cent coins that add upto $2. How many 50 cent coins does she have?

Peapot is right, this question can be easily solved by guess and check.

Do a table and start with
50 cts x 1 = $0.50
20 cts x 6 = $1.20
10 cts x 1 = $0.10
8 coins but $1.80, short of $0.20

50cts x 2 = $1
20cts x 4 = $0.80
10cts x 2 = $0.20
so 8 coins and $2 and he has 2 50 cts coins

[HAPPYH]

ksi:

HAPPYH:

[quote=\"Michaelia0816\"]Not possible, to use three, but after comparing two and found one of it, use it for another to compare.

Could you please help me solve the following problem using the above method? Thank you in advance.

Si Rong had 8 50 cent-coins, 20 cent coins and 10 cent coins that add upto $2. How many 50 cent coins does she have?

Peapot is right, this question can be easily solved by guess and check.

Do a table and start with
50 cts x 1 = $0.50
20 cts x 6 = $1.20
10 cts x 1 = $0.10
8 coins but $1.80, short of $0.20

50cts x 2 = $1
20cts x 4 = $0.80
10cts x 2 = $0.20
so 8 coins and $2 and he has 2 50 cts coins[/quote]Thank you KSI. Just curious to know whether any formula can be applied for this.

[HAPPYH]

peapot:

If three items then need to use guess and check. This was what I was told by the school teacher.

Thank you peapot. I am bit worried because if the numbers get bigger, then my DD will have a problem with guess and check. Or she will take very long to derive the answer.