Finding the Fourth Proportional to 139.00, 208.49 and 78.10

Step by Step Solution

1. Step 1: Write the proportion equation
   139.00 : 208.49 = 78.10 : x
2. Step 2: Convert to fraction form
   139.00/208.49 = 78.10/x
3. Step 3: Cross multiply
   139.00x = 208.49 × 78.10
4. Step 4: Simplify right side
   139.00x = 16,283.15
5. Step 5: Solve for x
   x = 16,283.15/139.00
6. Step 6: Final answer
   x = 117.14