Finding the Fourth Proportional to 139.18, 208.37 and 78.23

Step by Step Solution

1. Step 1: Write the proportion equation
   139.18 : 208.37 = 78.23 : x
2. Step 2: Convert to fraction form
   139.18/208.37 = 78.23/x
3. Step 3: Cross multiply
   139.18x = 208.37 × 78.23
4. Step 4: Simplify right side
   139.18x = 16,300.39
5. Step 5: Solve for x
   x = 16,300.39/139.18
6. Step 6: Final answer
   x = 117.12