Finding the Fourth Proportional to 99.92, 137.85 and 78.15

Step by Step Solution

1. Step 1: Write the proportion equation
   99.92 : 137.85 = 78.15 : x
2. Step 2: Convert to fraction form
   99.92/137.85 = 78.15/x
3. Step 3: Cross multiply
   99.92x = 137.85 × 78.15
4. Step 4: Simplify right side
   99.92x = 10,772.98
5. Step 5: Solve for x
   x = 10,772.98/99.92
6. Step 6: Final answer
   x = 107.82