Finding the Fourth Proportional to 99.50, 137.21 and 78.74

Step by Step Solution

1. Step 1: Write the proportion equation
   99.50 : 137.21 = 78.74 : x
2. Step 2: Convert to fraction form
   99.50/137.21 = 78.74/x
3. Step 3: Cross multiply
   99.50x = 137.21 × 78.74
4. Step 4: Simplify right side
   99.50x = 10,803.86
5. Step 5: Solve for x
   x = 10,803.86/99.50
6. Step 6: Final answer
   x = 108.58