Problems Involving Two Variables Concept

Dear Sunny,

I have encountered a math's problem for primary 6, could you please advise me how to solve it?

There were a total of 820 boys and girls at a funfair. After 3/4 of the boys and 3/5 of the girls left the funfair, there were 120 more girls than boys remaining behind. How many boys were there at the funfair at first?

Thanks for your help

Yani

From the Desk of Sunny Tan........

Questions for UTM readers to attempt?

Posted to all UTM publication readers,

Any UTM readers keen to to attempt the following?
Do post your answers in this blog for discussion.

Clue:
Q1) Chapter 6: Proportion Concept
Q2) Chapter 5: Two Variable Concept
Q3) Chapter 3: Repeated Identity
Q4) Chapter 1.4: Before & After (All changing quantities)


Hi Mr Sunny

Could UTM be used for the following problems?

1) A group of 24 children sold some tickets for a charity show. Each ticket was sold at $5. Each boy sold 5 tickets and each girl sold 3 tickets. The boys collected $40 more than the girls.(a) How many girls were there in the group?(b) How many tickets were sold altogether?

2) There are 85 plates of fried rice for 80 people. Each adult eats 2 plates of fried rice and every three children share 1 plate of fried rice. How many adults and children are there?

3) Four girls, A, B, C and D, each have some stamps. The number of stamps A has is 1/2 of the total number of stamps B, C and D have. The number of B has is 1/3 of the total number of A, C and D have. The number of stamps C has is 1/4 of the total number of stamps A, B and D have. If D has 78 stamps, find the total number of stamps A & B have altogether.

4) At first, Jane had 2/3 as many stamps as Kelly. After Jane bought another 20 stamps and Kelly lost 29 stamps, Jane now has 4/5 as many stamps as Kelly. Find the number of stamps Kelly had at first.

Best Wishes

PSLE Parents

Can these problems be solved by UTM? - Mrs Sui

Q1) In Hall A, 30% of the 800 people were men. In Hall B 40% of the 400 people were women and children. After some of the people in both hall had switched hall, 25% of the people in Hall A and 75% of those in hall B were men. How many people were there in Hall B after the change?


Q2)During a warehouse book sale, Sally spent 62.5% of her money on 24 books and 18 pens. She also spent 25% of her remaining money on 18 files. Each pen costs 8/9 as much as the price of one book. The file costs $7.80 less than a book. Find the total cost of one book and one pen.


Question posted by Mrs Sui, UTM book reader
Tues, 24th Feb 2009


From the desk of Sunny Tan ... ...

Q1)This concept is covered in UTM book, Chapter 1.2 –Before and After (Total unchanged)
with Chapter 5 – Two variables concept.

i) The total number of men in Hall A and Hall B remain unchanged before and after the transfer.
ii) The total number of women and children in Hall A and Hall B remain unchanged before and after the transfer.
iii) The total number of people in Hall A and Hall B remain unchanged before and after the transfer.

2) The UTM concept to solve this question is covered in Chapter 6 - Proportion Concept.