Average weight of a group; one person leaves and the average drops: weight of the one who left

The same question, asked 3 times: 21 Jul 2023 S3*, 15 Sep 2025 S1*, 17 Sep 2025 S2. Every wording below, oldest first.

Try each one first, then open its answer.

Question 1
21 Jul 2023 S3
54 $There are 15 students in a class. Their average weight is 40 kg. When one student leaves the class, the average weight is 39.5 kg. What is the weight of the student who left the class (where kg means kilogram)?$
Tap an option to check your answer.
Question 2
15 Sep 2025 S1
57 $The average weight of 12 people is 65 kg. If one person leaves and the new average becomes 64.5 kg, what is the weight of the person who left?$
Tap an option to check your answer.
Question 3
17 Sep 2025 S2
55 $The average weight of 30 students is 60 kg. If one student is removed, the average drops to 59.5 kg. What is the weight of the removed student?$
Tap an option to check your answer.

Question 1