A tailor used 30 buttons that had an average weight of x grams per button and 20 other buttons that had an average weight of 80 grams per button. Which of the following is the average weight per button, in grams, of the 50 buttons that the tailor used?

Question

vivek3461 · Answer

Just try it in a simple way.
Average weight of 'n' elements = Total weight of 'n' elements / 'n'
 So for your problem  average  = (30*x + 20*80) / 50