Finding the Fourth Proportional to 1,321.17, 1,978.71 and 773.20

Step by Step Solution

1. Step 1: Write the proportion equation
   1,321.17 : 1,978.71 = 773.20 : x
2. Step 2: Convert to fraction form
   1,321.17/1,978.71 = 773.20/x
3. Step 3: Cross multiply
   1,321.17x = 1,978.71 × 773.20
4. Step 4: Simplify right side
   1,321.17x = 1,529,938.57
5. Step 5: Solve for x
   x = 1,529,938.57/1,321.17
6. Step 6: Final answer
   x = 1,158.02