Out of a class of 64 people ,7 people of average weight 61 kg leave, and immediately 3 people weighing 70kg ,77 kg and 68 kg join. there by making the new average weight of the class 69 kg. What was the original average weight of the class of 64 people?Options9059677068

To solve this problem, we need to follow these steps:

1. First, we need to calculate the total weight of the 7 people who left the class. This is done by multiplying the average weight of these 7 people by the number of people. So, 7 people * 61 kg/person = 427 kg.

2. Then, we need to calculate the total weight of the 3 people who joined the class. This is done by adding the weights of these 3 people. So, 70 kg + 77 kg + 68 kg = 215 kg.

3. Now, we need to calculate the total weight of the class after the changes. This is done by multiplying the new average weight by the new number of people in the class. So, 69 kg/person * 60 people = 4140 kg.

4. Then, we need to calculate the total weight of the class before the changes. This is done by adding the total weight of the people who left to the total weight after the changes, and then subtracting the total weight of the people who joined. So, 427 kg + 4140 kg - 215 kg = 4352 kg.

5. Finally, we need to calculate the original average weight of the class. This is done by dividing the total weight before the changes by the original number of people in the class. So, 4352 kg / 64 people = 68 kg/person.

So, the original average weight of the class of 64 people was 68 kg.