Question

A gym is offering free membership for a month to the first person who can guess the weight of a mystery duumbbells'. Within the mystery, duumbbells' is a metal block that weighs between 1 and 40 kilograms. Outside the room with the mystery duumbbells' are an assortment of duumbbells of known whole-number weights, and inside the room is a standard weighing scale and the mystery duumbbell. You are allowed to select and take with you any four weights from the collection outside and use only those to determine the weight of the mystery duumbbell.
What is the sum of the four weights you should take into the room?

Answer 1

Your answer is 40kg

I hope this is right