Finding the Fourth Proportional to 139.35, 209.00 and 58.15

Step by Step Solution

1. Step 1: Write the proportion equation
   139.35 : 209.00 = 58.15 : x
2. Step 2: Convert to fraction form
   139.35/209.00 = 58.15/x
3. Step 3: Cross multiply
   139.35x = 209.00 × 58.15
4. Step 4: Simplify right side
   139.35x = 12,153.43
5. Step 5: Solve for x
   x = 12,153.43/139.35
6. Step 6: Final answer
   x = 87.21