Finding the Fourth Proportional to 78.29, 117.39 and 42.20

Step by Step Solution

1. Step 1: Write the proportion equation
   78.29 : 117.39 = 42.20 : x
2. Step 2: Convert to fraction form
   78.29/117.39 = 42.20/x
3. Step 3: Cross multiply
   78.29x = 117.39 × 42.20
4. Step 4: Simplify right side
   78.29x = 4,953.86
5. Step 5: Solve for x
   x = 4,953.86/78.29
6. Step 6: Final answer
   x = 63.28