Finding the Fourth Proportional to 100.62, 139.05 and 90.72

Step by Step Solution

1. Step 1: Write the proportion equation
   100.62 : 139.05 = 90.72 : x
2. Step 2: Convert to fraction form
   100.62/139.05 = 90.72/x
3. Step 3: Cross multiply
   100.62x = 139.05 × 90.72
4. Step 4: Simplify right side
   100.62x = 12,614.62
5. Step 5: Solve for x
   x = 12,614.62/100.62
6. Step 6: Final answer
   x = 125.37