Question

To measures and take 31 kg of rice from a 100 kg rice bag in minimum number of weighing using a pan blance which pair will you choose?

Answer 1

Since we are free to choose drop weight, but are limited in measurements (two), then it is rational to use 24 kg drop weight and do the following measurements:
1. Add a 24 kg drop weight to one basin, tip rice into basins and bring them to balance by means of our device (62 kg and 38+24 kg)
2. Split the 62 kg pile into two equal parts (31 kg and 31 kg)