Finding the Fourth Proportional to 100.55, 138.88 and 72.87

Step by Step Solution

1. Step 1: Write the proportion equation
   100.55 : 138.88 = 72.87 : x
2. Step 2: Convert to fraction form
   100.55/138.88 = 72.87/x
3. Step 3: Cross multiply
   100.55x = 138.88 × 72.87
4. Step 4: Simplify right side
   100.55x = 10,119.82
5. Step 5: Solve for x
   x = 10,119.82/100.55
6. Step 6: Final answer
   x = 100.65