Finding the Fourth Proportional to 100.76, 139.10 and 78.58

Step by Step Solution

1. Step 1: Write the proportion equation
   100.76 : 139.10 = 78.58 : x
2. Step 2: Convert to fraction form
   100.76/139.10 = 78.58/x
3. Step 3: Cross multiply
   100.76x = 139.10 × 78.58
4. Step 4: Simplify right side
   100.76x = 10,930.48
5. Step 5: Solve for x
   x = 10,930.48/100.76
6. Step 6: Final answer
   x = 108.48