Finding the Fourth Proportional to 100.23, 138.37 and 78.15

Step by Step Solution

1. Step 1: Write the proportion equation
   100.23 : 138.37 = 78.15 : x
2. Step 2: Convert to fraction form
   100.23/138.37 = 78.15/x
3. Step 3: Cross multiply
   100.23x = 138.37 × 78.15
4. Step 4: Simplify right side
   100.23x = 10,813.62
5. Step 5: Solve for x
   x = 10,813.62/100.23
6. Step 6: Final answer
   x = 107.89