Finding the Fourth Proportional to 100.59, 150.15 and 86.91

Step by Step Solution

1. Step 1: Write the proportion equation
   100.59 : 150.15 = 86.91 : x
2. Step 2: Convert to fraction form
   100.59/150.15 = 86.91/x
3. Step 3: Cross multiply
   100.59x = 150.15 × 86.91
4. Step 4: Simplify right side
   100.59x = 13,049.54
5. Step 5: Solve for x
   x = 13,049.54/100.59
6. Step 6: Final answer
   x = 129.73