Q&A - P3 Math

[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.

[chowon]

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!!

I found that drawing out the model really helpful in solving problems relating to age. Give it a try.

[fohope]

Hi,

Pls help to solve the problem sum. Thank in advance.

A group of classmates plan to buy a present for their teacher. If each of them pay sgd2.00, they will be short of sgd3.00 for the present.
If each of them pay sgd3.00,they will have an extra of sgd3.00. If there are fewer than 10 classmates, how much does the present cost ?

[buds]

Sharon is thinking of a number between 300 and 400. When she divides it by 6 or 8, it leaves a remainder of 5. What *number is she thinking of?


*There’s more than one possible answer…

[smartmummy]

fohope:

Hi,

Pls help to solve the problem sum. Thank in advance.

A group of classmates plan to buy a present for their teacher. If each of them pay sgd2.00, they will be short of sgd3.00 for the present.
If each of them pay sgd3.00,they will have an extra of sgd3.00. If there are fewer than 10 classmates, how much does the present cost ?

Time table 2: 2 4 6 8 10 12 14 16 18
+3: 5 7 9 11 13 15 17 19 21
Time table 3:3 6 9 12 15 18 21 24 27
-3 : 0 3 6 9 12 15
Price is sgd 9