Finding the Fourth Proportional to 143.31, 215.34 and 139.05

Step by Step Solution

1. Step 1: Write the proportion equation
   143.31 : 215.34 = 139.05 : x
2. Step 2: Convert to fraction form
   143.31/215.34 = 139.05/x
3. Step 3: Cross multiply
   143.31x = 215.34 × 139.05
4. Step 4: Simplify right side
   143.31x = 29,943.03
5. Step 5: Solve for x
   x = 29,943.03/143.31
6. Step 6: Final answer
   x = 208.94