Finding the Fourth Proportional to 100.48, 138.50 and 78.61

Step by Step Solution

1. Step 1: Write the proportion equation
   100.48 : 138.50 = 78.61 : x
2. Step 2: Convert to fraction form
   100.48/138.50 = 78.61/x
3. Step 3: Cross multiply
   100.48x = 138.50 × 78.61
4. Step 4: Simplify right side
   100.48x = 10,886.99
5. Step 5: Solve for x
   x = 10,886.99/100.48
6. Step 6: Final answer
   x = 108.36