3 boxes have some average weight.When one box which weighs 89 kg is replaced by another box,the average weight increases by 5 kg. How much the new box weighs?109 kg94 kg104 kg84 kg

Let's solve this step by step:

1. Let's assume the average weight of the 3 boxes before the replacement was 'x' kg. So, the total weight of the 3 boxes was 3x kg.

2. When one box of 89 kg is replaced, the average weight increases by 5 kg. So, the new average weight is 'x+5' kg. Therefore, the total weight of the 3 boxes now is 3(x+5) kg.

3. The total weight before and after the replacement remains the same except for the weight of the replaced box. So, we can set up the following equation:

   3x + 89 = 3(x+5)

4. Simplifying the equation gives:

   3x + 89 = 3x + 15

5. Subtracting 3x from both sides gives:

   89 = 15

6. This is a contradiction, which means our initial assumption that the total weight remains the same is incorrect. In fact, the total weight increases by the weight of the new box.

7. So, the correct equation should be:

   3x + weight of new box = 3(x+5)

8. We know that the weight of the new box is more than 89 kg. Let's denote the weight of the new box as '89 + y'. Substituting this into the equation gives:

   3x + 89 + y = 3(x+5)

9. Simplifying the equation gives:

   y = 15

10. Therefore, the weight of the new box is 89 + 15 = 104 kg.

So, the correct answer is 104 kg.