Christmas MT's answer to Jasper's Primary 5 Maths Percentage Singapore question.
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No, the answer is not 120.
The question asks "How many red chairs must be added to the concert hall so that the number of red chairs is 20% of the total number of chairs after that?"
You cannot just add 10% to make it 20%. By doing so, you did not take into account the total number of chairs afterwards. Percentage is about the ratio to the total. As you add the red chairs, the total changes so does the percentage.
Easy way to check is, assuming your answer 120 is correct, try to calculate the percentage of red chairs now, does it give you 20%?
R% = (120+120) / (1200+120) * 100% = 18.18%
Hope this helps.
The question asks "How many red chairs must be added to the concert hall so that the number of red chairs is 20% of the total number of chairs after that?"
You cannot just add 10% to make it 20%. By doing so, you did not take into account the total number of chairs afterwards. Percentage is about the ratio to the total. As you add the red chairs, the total changes so does the percentage.
Easy way to check is, assuming your answer 120 is correct, try to calculate the percentage of red chairs now, does it give you 20%?
R% = (120+120) / (1200+120) * 100% = 18.18%
Hope this helps.
Date Posted:
2 years ago
Many thanks for the clue.
Is the answer 150?
120+150=270/1350=20%.
I am still learning Percentage topic. What is the method to reach 150 if it is correct? I simply adding to the right %.
Is the answer 150?
120+150=270/1350=20%.
I am still learning Percentage topic. What is the method to reach 150 if it is correct? I simply adding to the right %.
Any formula method I can use?
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