Finding the Fourth Proportional to 82.20, 123.31 and 28.09

Step by Step Solution

1. Step 1: Write the proportion equation
   82.20 : 123.31 = 28.09 : x
2. Step 2: Convert to fraction form
   82.20/123.31 = 28.09/x
3. Step 3: Cross multiply
   82.20x = 123.31 × 28.09
4. Step 4: Simplify right side
   82.20x = 3,463.78
5. Step 5: Solve for x
   x = 3,463.78/82.20
6. Step 6: Final answer
   x = 42.14