Finding the Fourth Proportional to 87.91, 131.91 and 42.31

Step by Step Solution

1. Step 1: Write the proportion equation
   87.91 : 131.91 = 42.31 : x
2. Step 2: Convert to fraction form
   87.91/131.91 = 42.31/x
3. Step 3: Cross multiply
   87.91x = 131.91 × 42.31
4. Step 4: Simplify right side
   87.91x = 5,581.11
5. Step 5: Solve for x
   x = 5,581.11/87.91
6. Step 6: Final answer
   x = 63.49