Finding the Fourth Proportional to 78.24, 117.21 and 42.12

Step by Step Solution

1. Step 1: Write the proportion equation
   78.24 : 117.21 = 42.12 : x
2. Step 2: Convert to fraction form
   78.24/117.21 = 42.12/x
3. Step 3: Cross multiply
   78.24x = 117.21 × 42.12
4. Step 4: Simplify right side
   78.24x = 4,936.89
5. Step 5: Solve for x
   x = 4,936.89/78.24
6. Step 6: Final answer
   x = 63.10