Shawn's answer to Kc's Primary 5 Maths Whole Numbers Singapore question.
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There are 2 methods in doing this.
Method 1,
Initially the average of 39 students is 69, after correcting the mark of 1 student, the new average is 70. From here we can say that the average increased by 1. So that student’s mark actually contribute 1 mark to all 39 students to make the average go up by 1. His actual mark is 53 + 39 = 92.
Method 2,
Initial total marks for 39 students = 39 x 69 = 2691
New total after correcting = 39 x 70 = 2730
Total went up by 2730 - 2691 = 39 marks
53 + 39 = 92
Method 1,
Initially the average of 39 students is 69, after correcting the mark of 1 student, the new average is 70. From here we can say that the average increased by 1. So that student’s mark actually contribute 1 mark to all 39 students to make the average go up by 1. His actual mark is 53 + 39 = 92.
Method 2,
Initial total marks for 39 students = 39 x 69 = 2691
New total after correcting = 39 x 70 = 2730
Total went up by 2730 - 2691 = 39 marks
53 + 39 = 92
Date Posted:
5 years ago
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