Finding the Fourth Proportional to 100.79, 139.15 and 77.43

Step by Step Solution

1. Step 1: Write the proportion equation
   100.79 : 139.15 = 77.43 : x
2. Step 2: Convert to fraction form
   100.79/139.15 = 77.43/x
3. Step 3: Cross multiply
   100.79x = 139.15 × 77.43
4. Step 4: Simplify right side
   100.79x = 10,774.38
5. Step 5: Solve for x
   x = 10,774.38/100.79
6. Step 6: Final answer
   x = 106.90