Finding the Fourth Proportional to 78.90, 118.17 and 42.72

Step by Step Solution

1. Step 1: Write the proportion equation
   78.90 : 118.17 = 42.72 : x
2. Step 2: Convert to fraction form
   78.90/118.17 = 42.72/x
3. Step 3: Cross multiply
   78.90x = 118.17 × 42.72
4. Step 4: Simplify right side
   78.90x = 5,048.22
5. Step 5: Solve for x
   x = 5,048.22/78.90
6. Step 6: Final answer
   x = 63.98