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The mean of 20 observations is 32. It was detected that one observation 43 was wrongly copied as 33. Find the correct mean. - Mathematics

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Question

The mean of 20 observations is 32. It was detected that one observation 43 was wrongly copied as 33. Find the correct mean.

Sum
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Solution

Given: Mean of 20 observations = 32; one observation 43 was wrongly copied as 33.

Step-wise calculation:

1. Total (incorrect) sum

= 20 × 32

= 640

2. Correct sum

= 640 – 33 + 43 

= 650

3. Correct mean

= 650 ÷ 20

= 32.5

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Chapter 15: Statistics - Exercise 15C [Page 303]

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Nootan Mathematics [English] Class 9 ICSE
Chapter 15 Statistics
Exercise 15C | Q 9. | Page 303
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