Finding the Fourth Proportional to 100.80, 139.31 and 83.31

Step by Step Solution

1. Step 1: Write the proportion equation
   100.80 : 139.31 = 83.31 : x
2. Step 2: Convert to fraction form
   100.80/139.31 = 83.31/x
3. Step 3: Cross multiply
   100.80x = 139.31 × 83.31
4. Step 4: Simplify right side
   100.80x = 11,605.50
5. Step 5: Solve for x
   x = 11,605.50/100.80
6. Step 6: Final answer
   x = 115.13