Hi Parika,I'm unable to get your formula, Mention the name of our e-book, if it is given anywhere,The solution for this can be given as (old quantity*old average) - (new average*new quantity) = (50*45) - (44.9*49) = 49.9.I hope this helps you, please close the ticket if your query has been resolved.

WhatsApp Image 2025-05-15 at 14.03.45.jpeg 78.93 KB

WhatsApp Image 2025-05-15 at 14.03.45.jpeg 78.93 KB

Im talking about this formula

Im talking about this formula

IMG20250515143027.jpg 3.91 MB

Im not able to understand this approach There are 50 boys in a class. Their average weight is 45 kg. When one boy leaves the class, the average reduces by 100 g. Find the weight of the boy who left the class.By using this formula :Change in quantities * old average (+-) change in average * new quantity Im getting a negative 40.1 Kg value which is incorrect.Am I using the formula wrong or where am i going wrong because this is a shortcut formula and it is applying well in the cases where the weight is added or the quantities are increasing , but when the quantities are decreasing, I unable to apply the same formula.

Im not able to understand this approach There are 50 boys in a class. Their average weight is 45 kg. When one boy leaves the class, the average reduces by 100 g. Find the weight of the boy who left the class.By using this formula :Change in quantities * old average (+-) change in average * new quantity Im getting a negative 40.1 Kg value which is incorrect.Am I using the formula wrong or where am i going wrong because this is a shortcut formula and it is applying well in the cases where the weight is added or the quantities are increasing , but when the quantities are decreasing, I unable to apply the same formula.