Finding the Fourth Proportional to 91,915.31, 137,989.62 and 78,151.79

Step by Step Solution

1. Step 1: Write the proportion equation
   91,915.31 : 137,989.62 = 78,151.79 : x
2. Step 2: Convert to fraction form
   91,915.31/137,989.62 = 78,151.79/x
3. Step 3: Cross multiply
   91,915.31x = 137,989.62 × 78,151.79
4. Step 4: Simplify right side
   91,915.31x = 10,784,135,114.47
5. Step 5: Solve for x
   x = 10,784,135,114.47/91,915.31
6. Step 6: Final answer
   x = 117,326.87