Finding the Fourth Proportional to 100.89, 139.25 and 61.57

Step by Step Solution

1. Step 1: Write the proportion equation
   100.89 : 139.25 = 61.57 : x
2. Step 2: Convert to fraction form
   100.89/139.25 = 61.57/x
3. Step 3: Cross multiply
   100.89x = 139.25 × 61.57
4. Step 4: Simplify right side
   100.89x = 8,573.62
5. Step 5: Solve for x
   x = 8,573.62/100.89
6. Step 6: Final answer
   x = 84.98