Q&A - P3 Math

[MathIzzzFun]

AgonyMum:

Hi,

What is the fastest and most efficient of solving questions like this one:

pen+pencil+eraser=630g
pen+ruler +pencil=730g
eraser +pencil+ruler=330g
pen+eraser+ruler=800g
What is the value of pen+pencil+eraser+ruler?
Is simult. equation with substitution the fastest way?
I tried to solve it and although it can be done, it is pretty tedious.

TQ in advance.

Hi

add all to get 3 sets of (pencil, eraser, ruler,pen) and divide by 3.

cheers.

[AgonyMum]

Oh yah! Got it.You really make it seems so easy!

Thanks a million,MathIzzzFun

[BigDevil]

Hi AgonyMum,


Please post your future Math questions in the http://www.kiasuparents.com/kiasu/forum/viewtopic.php?f=66&t=149 thread.

This thread will soon be merged with the Q&A thread.

Thank you.

[AgonyMum]

Hi BigDevil, apologies for posting in the wrong thread.Will post at P3 Math in future.

[MathIzzzFun]

AgonyMum:

Hi MathIzzzFun,

Am still trying to figure out Qn 3 and 4 but the good news is my child has understood Qn 1 and 2....All thanks to you!

Hi

Q3 ... solution in pictorial

http://tinyurl.com/mathizzzfun-20120426workback01

cheers.

[yuanyuan mama]

Hi,


Below is the question given by my child's teacher in a Math exercise:

In a class of 42 pupils, each boy received 3 stickers and each girl received 4 stickers from teacher. Altogether, the teacher gave out 154 stickers. How many girls were there in this class?

I know how to solve by guess and check but not the solution below (given by teacher).

42 (tot pupils) X 3 (stickers for each boy) = 126
154 (tot stickers given out) - 126 = 28
ANSWER: 28 girls in the class

Can someone help to explain why 42 X 3 and not X 4 (sticker for each gal)? And why 28 is the number of gals, not stickers received by gals? Does this formula always work for guess and check question?

Hope someone may enlighten me. Thanks.

[lynntan15]

There are total 42 students.


Boy –> 3 stickers
Girl —> 3 stickers + 1 stickers

Therefore 3 x 42 = 126

Remaining (154-126) = 28 extra 1 stickers given to each girl.

Therefore, there are 28 girls and 14 boys

Check : 14 x 3 +28 x 4 = 42 + 112 = 154 stickers in total.

[peapot]

Hi, can help me with this P3 question?


Father is 5 times as old as Calvin now. In 10 years’ time, their total age will be 74 years old. How old is Calvin now?

I m always confused with these "age" problem sum.

Another "age" question. Mr Tan is 42 years old and his son is 8 years old now. In how many years time will Mr Tan be twice as old as his son?

Pls enlighten me. Thanks!!

[MathIzzzFun]

peapot:

Hi, can help me with this P3 question?


Father is 5 times as old as Calvin now. In 10 years' time, their total age will be 74 years old. How old is Calvin now?

I m always confused with these \"age\" problem sum.

Another \"age\" question. Mr Tan is 42 years old and his son is 8 years old now. In how many years time will Mr Tan be twice as old as his son?

Pls enlighten me. Thanks!!

Hi

Q1.Father is 5 times as old as Calvin now. In 10 years' time, their total age will be 74 years old. How old is Calvin now?

In 10 years' time, both will be older by 10 years, ie total age will increase by 10 + 10 = 20. So, total age now = 74 - 20 = 54
Calvin's age now = 54/6 = 9

Q2. Mr Tan is 42 years old and his son is 8 years old now. In how many years time will Mr Tan be twice as old as his son?

The age difference will remain the same.

Age difference = 42 - 8 = 34

When Mr Tan is twice as old as his son, and since the age difference is 34, Mr Tan will be 2 x 34 = 68
68 - 42 = 26 --> Mr Tan will be twice his son's age in 26 years' time.

cheers.

[ttlkbs]

Now

Calvin => 1 unit
Father => 5 units
10 years time
Calvin => 1 unit + 10
Father => 5 units + 10

Calvin’s age + Father’s age = 74
6 units + 20 = 74
6 units = 54
1 unit = 9

Calvin is 9 yrs old now.