Finding the Fourth Proportional to 78.84, 118.31 and 42.78

Step by Step Solution

1. Step 1: Write the proportion equation
   78.84 : 118.31 = 42.78 : x
2. Step 2: Convert to fraction form
   78.84/118.31 = 42.78/x
3. Step 3: Cross multiply
   78.84x = 118.31 × 42.78
4. Step 4: Simplify right side
   78.84x = 5,061.30
5. Step 5: Solve for x
   x = 5,061.30/78.84
6. Step 6: Final answer
   x = 64.20