Finding the Fourth Proportional to 100.82, 139.04 and 90.42

Step by Step Solution

1. Step 1: Write the proportion equation
   100.82 : 139.04 = 90.42 : x
2. Step 2: Convert to fraction form
   100.82/139.04 = 90.42/x
3. Step 3: Cross multiply
   100.82x = 139.04 × 90.42
4. Step 4: Simplify right side
   100.82x = 12,572.00
5. Step 5: Solve for x
   x = 12,572.00/100.82
6. Step 6: Final answer
   x = 124.70