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5 Common Mistakes in Primary 5 Maths Ratio Questions and How to Avoid Them

Updated: Mar 21


Primary 5 Maths Ratio Questions

Primary 5 maths ratio questions play a crucial role in developing students' understanding of mathematical concepts. However, common mistakes can hinder their progress and lead to inaccuracies in problem-solving. In this article, we will delve into 5 common mistakes often encountered in primary 5 maths ratio questions and provide valuable tips on how to avoid them.


1. Ignoring Units or Mixing Different Units


Mistake: Using Different Units Without Converting Them

One prevalent error in primary school maths ratio problems involves ignoring units or mixing different units without proper conversion. This occurs when quantities are expressed in disparate units, such as metres and centimetres, kilograms and grams, or dollars and cents.


Example:


Express 50 g to 2 kg.


The common mistake is answering 50 : 2. That would be incorrect because we have to convert both sides to either grams or kilograms.


Correct Answer:


2 kg = 2000 g


50 : 2000 = 1 : 40


Tip: Always remember to check that both quantities are of the same units before expressing them as ratios.


Ignoring Units or Mixing Different Units

2. Not Simplifying Ratio


Mistake: Neglecting to Simplify a Ratio Not Expressed in Fraction Form

A common error is that if a ratio is not written in fraction form, we forget to simplify it. Leaving the final answer as 6:8 is a typical mistake, as 6 : 8 is not in its simplest form.

 

Example:


Leaving the final answer as 6 : 8.


That would be incorrect because 6:8 is not the simplest form.


Correct Answer:


Simplifying the ratio,


6 : 8

= 3 : 4


Tip: Always remember that the final answer must always be in the simplest form!


3. Ratio in the Wrong Order


Mistake: Expressing the Ratio in the Wrong Order

Another mistake involves giving the ratio based on the order of the numbers that appear in the question. This can lead to inaccuracies in the final result.


Example:


Tony has $12 and Freddy has $30. What is the ratio of Freddy's money to Tony's money?


The common mistake is expressing the ratio as 12 : 30. That would be incorrect because the question asks for Freddy’s money to Tony’s money.


Correct Answer:

Freddy : Tony

30 : 12

= 5 : 2


Tip: Place the names of the variables at the top so that you can easily reference them when inputting the appropriate values into the corresponding variables.


Not Simplifying Ratio

4. Not Reading the Question Properly


Mistake: Giving the Wrong Variable as the Answer

A frequent mistake in primary 5 maths ratio questions is not reading the question carefully, leading to errors in selecting the correct variable for the ratio.


Example:


Dan used 60 blue tiles, 48 red tiles, and 24 green tiles to design a project. Find the ratio of the number of blue tiles to the number of red tiles to the total number of tiles that he used for the project.


The common mistake is expressing the ratio as 60 : 48 : 24. That would be incorrect because the question asks for blue to red to the total number of tiles.


Correct Answer:


60 + 48 + 24 = 132


Simplifying the ratio,


60 : 48 : 132

= 5 : 4 : 11


Tip: Always read the question carefully and circle the variable in the ratio requested.


5. Using the Wrong Ratio


Mistake: Using Units in the Original Given Ratio Instead of the New Ratio

An error often encountered in complex ratio problems involves using units in the original given ratio instead of the new ratio obtained after manipulation.


Example:


In an examination hall, the ratio of the number of boys to the number of girls was 5 : 8. After 18 boys entered the hall, the new ratio of the number of boys to the number of girls became 2 : 3. How many children were there in the hall at first?


Solution:


At first          After

 B : G             B  :  G

 5 : 8                2  :  3

15 : 24              16 : 24


16 – 15 = 1

1 unit = 18



The common mistake is using the original given ratio 5 : 8 instead of the new ratio 15 : 24.


5 + 8 = 13

13 units = 13 × 18

              = 234


Correct Answer:

15 + 24 = 39

39 units = 39 × 18

             = 702



Tip: Always remember to use the ‘after’ ratio that has been converted instead


Not Reading the Question Properly

Understanding and avoiding these 5 common mistakes in Primary 5 Maths ratio questions is crucial for students to excel in their mathematical endeavours. By addressing these errors head-on, students can enhance their problem-solving skills and develop a solid foundation in ratio concepts. Teachers and parents play a pivotal role in guiding students to recognize and rectify these mistakes, fostering a positive and enriching learning experience in primary school mathematics.


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Unlock the key to your child's math success by enrolling them in AGrader's Primary Math Programme

At AGrader Learning Centre, our dedicated math tutors employ heuristics to teach problem-solving skills, empowering your child to tackle even the most mind-boggling problem sums with ease. Don't miss out on giving your child the tools they need for math excellence – enrol for AGrader’s Primary Math programme here.


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