Finding the Fourth Proportional to 87.85, 131.72 and 42.15

Step by Step Solution

1. Step 1: Write the proportion equation
   87.85 : 131.72 = 42.15 : x
2. Step 2: Convert to fraction form
   87.85/131.72 = 42.15/x
3. Step 3: Cross multiply
   87.85x = 131.72 × 42.15
4. Step 4: Simplify right side
   87.85x = 5,552.28
5. Step 5: Solve for x
   x = 5,552.28/87.85
6. Step 6: Final answer
   x = 63.20