Finding the Fourth Proportional to 1,003.80, 1,385.33 and 561.79

Step by Step Solution

1. Step 1: Write the proportion equation
   1,003.80 : 1,385.33 = 561.79 : x
2. Step 2: Convert to fraction form
   1,003.80/1,385.33 = 561.79/x
3. Step 3: Cross multiply
   1,003.80x = 1,385.33 × 561.79
4. Step 4: Simplify right side
   1,003.80x = 778,257.25
5. Step 5: Solve for x
   x = 778,257.25/1,003.80
6. Step 6: Final answer
   x = 775.31