Finding the Fourth Proportional to 78.15, 117.27 and 42.12

Step by Step Solution

1. Step 1: Write the proportion equation
   78.15 : 117.27 = 42.12 : x
2. Step 2: Convert to fraction form
   78.15/117.27 = 42.12/x
3. Step 3: Cross multiply
   78.15x = 117.27 × 42.12
4. Step 4: Simplify right side
   78.15x = 4,939.41
5. Step 5: Solve for x
   x = 4,939.41/78.15
6. Step 6: Final answer
   x = 63.20