Finding the Fourth Proportional to 42.56, 58.78 and 39.88

Step by Step Solution

1. Step 1: Write the proportion equation
   42.56 : 58.78 = 39.88 : x
2. Step 2: Convert to fraction form
   42.56/58.78 = 39.88/x
3. Step 3: Cross multiply
   42.56x = 58.78 × 39.88
4. Step 4: Simplify right side
   42.56x = 2,344.15
5. Step 5: Solve for x
   x = 2,344.15/42.56
6. Step 6: Final answer
   x = 55.08