Finding the Fourth Proportional to 78.17, 117.15 and 43.90

Step by Step Solution

1. Step 1: Write the proportion equation
   78.17 : 117.15 = 43.90 : x
2. Step 2: Convert to fraction form
   78.17/117.15 = 43.90/x
3. Step 3: Cross multiply
   78.17x = 117.15 × 43.90
4. Step 4: Simplify right side
   78.17x = 5,142.89
5. Step 5: Solve for x
   x = 5,142.89/78.17
6. Step 6: Final answer
   x = 65.79