Finding the Fourth Proportional to 108.86, 149.78 and 100.15

Step by Step Solution

1. Step 1: Write the proportion equation
   108.86 : 149.78 = 100.15 : x
2. Step 2: Convert to fraction form
   108.86/149.78 = 100.15/x
3. Step 3: Cross multiply
   108.86x = 149.78 × 100.15
4. Step 4: Simplify right side
   108.86x = 15,000.34
5. Step 5: Solve for x
   x = 15,000.34/108.86
6. Step 6: Final answer
   x = 137.80