Finding the Fourth Proportional to 100.90, 139.35 and 89.29

Step by Step Solution

1. Step 1: Write the proportion equation
   100.90 : 139.35 = 89.29 : x
2. Step 2: Convert to fraction form
   100.90/139.35 = 89.29/x
3. Step 3: Cross multiply
   100.90x = 139.35 × 89.29
4. Step 4: Simplify right side
   100.90x = 12,442.56
5. Step 5: Solve for x
   x = 12,442.56/100.90
6. Step 6: Final answer
   x = 123.32