One item removed and the average changes: find the removed item

This type of question, asked 7 times: 19 Jul 2023 S4, 21 Jul 2023 S3, 13 Sep 2025 S3, 15 Sep 2025 S1, 16 Sep 2025 S1, 17 Sep 2025 S2, 24 Sep 2025 S2. All 8 questions below, oldest first.

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Question 1
19 Jul 2023 S4
55 $The average of 8 numbers is 18. If one of the numbers is excluded, the average becomes 20. Find the excluded number.$
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Question 2
21 Jul 2023 S3
54 $There are 15 students in a class. Their average weight is 40 kg. When one student leaves the class, the average weight is 39.5 kg. What is the weight of the student who left the class (where kg means kilogram)?$
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Question 3
13 Sep 2025 S3
59 $10$
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Question 4
15 Sep 2025 S1
57 $The average weight of 12 people is 65 kg. If one person leaves and the new average becomes 64.5 kg, what is the weight of the person who left?$
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Question 5
16 Sep 2025 S1
57 $The average of 9 numbers is 56. When one number is removed, the average becomes 54. What number was removed?$
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Question 6
17 Sep 2025 S2
55 $The average weight of 30 students is 60 kg. If one student is removed, the average drops to 59.5 kg. What is the weight of the removed student?$
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Question 7
24 Sep 2025 S2
65 $The average of 9 numbers is 63. When one number is removed, the average becomes 60. What number was removed?$
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Question 8
24 Sep 2025 S2
63 $In a company, the average salary of 5 engineers is Rs. 60,000. If one engineer leaves and the average salary becomes Rs. 58,000, what was the salary of the engineer who left?$
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One item removed and the average changes: find the removed item

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Question 8