Finding the Fourth Proportional to 101.21, 139.50 and 71.72

Step by Step Solution

1. Step 1: Write the proportion equation
   101.21 : 139.50 = 71.72 : x
2. Step 2: Convert to fraction form
   101.21/139.50 = 71.72/x
3. Step 3: Cross multiply
   101.21x = 139.50 × 71.72
4. Step 4: Simplify right side
   101.21x = 10,004.94
5. Step 5: Solve for x
   x = 10,004.94/101.21
6. Step 6: Final answer
   x = 98.85