Finding the Fourth Proportional to 100.58, 138.78 and 76.10

Step by Step Solution

1. Step 1: Write the proportion equation
   100.58 : 138.78 = 76.10 : x
2. Step 2: Convert to fraction form
   100.58/138.78 = 76.10/x
3. Step 3: Cross multiply
   100.58x = 138.78 × 76.10
4. Step 4: Simplify right side
   100.58x = 10,560.46
5. Step 5: Solve for x
   x = 10,560.46/100.58
6. Step 6: Final answer
   x = 105.00