Finding the Fourth Proportional to 1,320.17, 1,978.72 and 579.56

Step by Step Solution

1. Step 1: Write the proportion equation
   1,320.17 : 1,978.72 = 579.56 : x
2. Step 2: Convert to fraction form
   1,320.17/1,978.72 = 579.56/x
3. Step 3: Cross multiply
   1,320.17x = 1,978.72 × 579.56
4. Step 4: Simplify right side
   1,320.17x = 1,146,778.47
5. Step 5: Solve for x
   x = 1,146,778.47/1,320.17
6. Step 6: Final answer
   x = 868.66