Finding the Fourth Proportional to 89.91, 124.10 and 57.15

Step by Step Solution

1. Step 1: Write the proportion equation
   89.91 : 124.10 = 57.15 : x
2. Step 2: Convert to fraction form
   89.91/124.10 = 57.15/x
3. Step 3: Cross multiply
   89.91x = 124.10 × 57.15
4. Step 4: Simplify right side
   89.91x = 7,092.32
5. Step 5: Solve for x
   x = 7,092.32/89.91
6. Step 6: Final answer
   x = 78.88