Finding the Fourth Proportional to 100.54, 138.72 and 89.74

Step by Step Solution

1. Step 1: Write the proportion equation
   100.54 : 138.72 = 89.74 : x
2. Step 2: Convert to fraction form
   100.54/138.72 = 89.74/x
3. Step 3: Cross multiply
   100.54x = 138.72 × 89.74
4. Step 4: Simplify right side
   100.54x = 12,448.73
5. Step 5: Solve for x
   x = 12,448.73/100.54
6. Step 6: Final answer
   x = 123.82