Finding the Fourth Proportional to 78.71, 118.15 and 42.71

Step by Step Solution

1. Step 1: Write the proportion equation
   78.71 : 118.15 = 42.71 : x
2. Step 2: Convert to fraction form
   78.71/118.15 = 42.71/x
3. Step 3: Cross multiply
   78.71x = 118.15 × 42.71
4. Step 4: Simplify right side
   78.71x = 5,045.49
5. Step 5: Solve for x
   x = 5,045.49/78.71
6. Step 6: Final answer
   x = 64.11