Finding the Fourth Proportional to 1,012.20, 1,517.91 and 318.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,012.20 : 1,517.91 = 318.72 : x
2. Step 2: Convert to fraction form
   1,012.20/1,517.91 = 318.72/x
3. Step 3: Cross multiply
   1,012.20x = 1,517.91 × 318.72
4. Step 4: Simplify right side
   1,012.20x = 483,788.28
5. Step 5: Solve for x
   x = 483,788.28/1,012.20
6. Step 6: Final answer
   x = 477.96