Finding the Fourth Proportional to 100.62, 138.84 and 78.78

Step by Step Solution

1. Step 1: Write the proportion equation
   100.62 : 138.84 = 78.78 : x
2. Step 2: Convert to fraction form
   100.62/138.84 = 78.78/x
3. Step 3: Cross multiply
   100.62x = 138.84 × 78.78
4. Step 4: Simplify right side
   100.62x = 10,937.82
5. Step 5: Solve for x
   x = 10,937.82/100.62
6. Step 6: Final answer
   x = 108.70