Finding the Fourth Proportional to 1,105.78, 1,656.37 and 521.28

Step by Step Solution

1. Step 1: Write the proportion equation
   1,105.78 : 1,656.37 = 521.28 : x
2. Step 2: Convert to fraction form
   1,105.78/1,656.37 = 521.28/x
3. Step 3: Cross multiply
   1,105.78x = 1,656.37 × 521.28
4. Step 4: Simplify right side
   1,105.78x = 863,432.55
5. Step 5: Solve for x
   x = 863,432.55/1,105.78
6. Step 6: Final answer
   x = 780.84