Finding the Fourth Proportional to 100.48, 138.59 and 78.31

Step by Step Solution

1. Step 1: Write the proportion equation
   100.48 : 138.59 = 78.31 : x
2. Step 2: Convert to fraction form
   100.48/138.59 = 78.31/x
3. Step 3: Cross multiply
   100.48x = 138.59 × 78.31
4. Step 4: Simplify right side
   100.48x = 10,852.98
5. Step 5: Solve for x
   x = 10,852.98/100.48
6. Step 6: Final answer
   x = 108.01