Finding the Fourth Proportional to 100.38, 138.47 and 72.71

Step by Step Solution

1. Step 1: Write the proportion equation
   100.38 : 138.47 = 72.71 : x
2. Step 2: Convert to fraction form
   100.38/138.47 = 72.71/x
3. Step 3: Cross multiply
   100.38x = 138.47 × 72.71
4. Step 4: Simplify right side
   100.38x = 10,067.10
5. Step 5: Solve for x
   x = 10,067.10/100.38
6. Step 6: Final answer
   x = 100.29