Finding the Fourth Proportional to 102.15, 152.60 and 90.72

Step by Step Solution

1. Step 1: Write the proportion equation
   102.15 : 152.60 = 90.72 : x
2. Step 2: Convert to fraction form
   102.15/152.60 = 90.72/x
3. Step 3: Cross multiply
   102.15x = 152.60 × 90.72
4. Step 4: Simplify right side
   102.15x = 13,843.42
5. Step 5: Solve for x
   x = 13,843.42/102.15
6. Step 6: Final answer
   x = 135.52