Math New Drill : Level 1 : Sum and Difference Problem2(2) ATOMIGAKUEN-2014

I bought same number of sheets of 50 yen stamp and 80 yen stamp, respectively.
The difference of the each total price was 540 yen.
How many sheets did I buy all together?


Answer
36 sheets

Solution
The difference of one sheet = 80 - 50 = 30 yen.
The number of sheet = 540 / 30 = 18.
Therefore total number = 18 × 2 = 36 sheets.