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p6 fractions (ling math)
Kelly spent 1/3 of her money on 5 pens and 11 erasers. The cost of each pen is 3 times the cost of each eraser. She bought some more pens with 3/4 of her remaining money. How many pens did she buy altogether?
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Fwd: 4 Must Know Concepts of Ratio
A Math Joke to Brighten Your Day
P5 and P6 Ratio word problems consists of many marks in the exam and your child cannot afford to lose them.
No matter how the questions twist and turn, here are 4 concepts which the questions will test.
Make Sure Your Child Know These 4 Concepts Very Well
1. Constant Part
Constant part means one of the parts remained the same while the other part changed.
In this case, you will need to make the part which remained the same to be equal to each other.
Example: Ali and Billy have money in the ratio of 5 : 6. After Billy spent $16, the ratio became 3 : 2. How much money does Billy have in the end?
Before:
A : B
= 5 : 6
= 15 : 18
After:
A : B
= 3: 2
= 15 : 10
18u – 10u = 8u
8u = $16
1u = $2
10u = $20 (Ans)
2. Constant Total
Constant Total means the total remained the same. Usually, this concept applies for question related to "Internal Transfer".
If A transfer an amount to B, A will decrease while B will increase by the same amount. So the total will stay the same.
Example: Ali and Billy have money in the ratio of 5 : 4. After Ali gave Billy $20, they have an equal amount of money. How much money does Billy have in the end?
Before:
A : B : Total
= 5 : 4 : 9
= 10 : 8 : 18
After:
A : B : Total
= 1 : 1 : 2
= 9 : 9 : 18
1 unit = $20
9 units = $180 (Ans)
3. Constant Difference
Constant Difference means the difference remained the same. Usually, this concept applies for question related to "Age".
As years go by, the age difference between 2 people will always be the same, because both will grow old together.
Example: The ages of Ali and Billy are in the ratio of 4 : 7. In 3 years time, their ages will be in the ratio of 3 : 5. How old is Billy now?
Before:
A : B : Difference
= 4 : 7 : 3
= 8 : 14 : 6
After:
A : B : Difference
= 3 : 5 : 2
= 9 : 15 : 6
1 unit = 3 years
14 units = 42 years old (Ans)
4. Everything Changed
As the name says, everything changed! Every part changed, the difference changed, the total changed… Nothing remained the same.
Another name for this method is called "Units and Parts".This type of questions are usually the last few 5 marks questions in the paper. So make sure your child know how to do this type of questions.
There are a few methods to solve this type of question. I will use an example below to show a method which you can use.
Example: The ratio of Ali's money to Billy's money was 2 : 1. After Ali saved another $60 and Billy spent $150, the ratio became 4 : 1. How much money did Ali have at first?
Step 1: Write down the starting ratio and apply the changes.
Before Change After A 2u +60 2u + 60 B 1u - 150 1u – 150
Step 2: Compare the final units with the final ratio.
A : B
= 2u + 60 : 1u – 150
= 4p : 1p
Step 3: Cross Multiply the final units with the final ratio
1 × (2u + 60) = 4 × (1u – 150)
2u + 60 = 4u – 600
Step 4: Solve for 1 unit
2 units = 60 + 600 = $660 (Ans)
These are the 4 must know concepts of PSLE Ratio. Make sure your child know when to apply the concept and how to use them correctly.
And these 4 concepts are only the tip of the iceberg.
There are lots of other key concepts which your child must know.
Stay Tuned for More Free Notes..
Yours Sincerely,
Jimmy Maths and Grade Solution Team
Simplifying Math Concepts
www.jimmymaths.com
P.S: Sharing is Caring. If you find this useful, feel free to forward this to someone you care about.
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