Chemistry related: How many grams of manganese is in the flask

An erlenmeyer flask contains 81.6 g of KMnO4. How many grams of manganese is in the flask?

thanks so much. could you explain it to me also. do you use percent composition thing?

Percent composition would work, but it's faster this way:

(81.6 g KMnO4) / (158.0341 g KMnO4/mol) x (1 mol Mn/1 mol KMnO4) x
(54.9380 g Mn/mol) = 28.4 g Mn