One member joins and the average changes: find the newcomer's value

This type of question, asked 4 times: 25 Jul 2023 S1, 14 Sep 2025 S2, 22 Sep 2025 S1, 23 Sep 2025 S2. All 4 questions below, oldest first.

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Question 1
25 Jul 2023 S1
53 $20^{\text{th}}$
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Question 2
14 Sep 2025 S2
58 $The average age of 40 students in a class is 16 years. When a new student is admitted, the average increases by 0.2 years. What is the age of the new student?$
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Question 3
22 Sep 2025 S1
64 $The average salary of 40 workers in a factory is Rs. 24,000. If the salary of a supervisor is added, the average rises to Rs. 24,500. What is the supervisor’s salary?$
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Question 4
23 Sep 2025 S2
67 $A student took 7 tests and had an average of 72. If his average after 8 tests increased to 73, what was his score on the 8th test?$
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Question 1