Finding the Fourth Proportional to 78.58, 117.87 and 42.58

Step by Step Solution

1. Step 1: Write the proportion equation
   78.58 : 117.87 = 42.58 : x
2. Step 2: Convert to fraction form
   78.58/117.87 = 42.58/x
3. Step 3: Cross multiply
   78.58x = 117.87 × 42.58
4. Step 4: Simplify right side
   78.58x = 5,018.90
5. Step 5: Solve for x
   x = 5,018.90/78.58
6. Step 6: Final answer
   x = 63.87