Finding the Fourth Proportional to 139.05, 208.13 and 78.00

Step by Step Solution

1. Step 1: Write the proportion equation
   139.05 : 208.13 = 78.00 : x
2. Step 2: Convert to fraction form
   139.05/208.13 = 78.00/x
3. Step 3: Cross multiply
   139.05x = 208.13 × 78.00
4. Step 4: Simplify right side
   139.05x = 16,233.10
5. Step 5: Solve for x
   x = 16,233.10/139.05
6. Step 6: Final answer
   x = 116.74