Finding the Fourth Proportional to 115.78, 159.89 and 100.16

Step by Step Solution

1. Step 1: Write the proportion equation
   115.78 : 159.89 = 100.16 : x
2. Step 2: Convert to fraction form
   115.78/159.89 = 100.16/x
3. Step 3: Cross multiply
   115.78x = 159.89 × 100.16
4. Step 4: Simplify right side
   115.78x = 16,014.83
5. Step 5: Solve for x
   x = 16,014.83/115.78
6. Step 6: Final answer
   x = 138.32