Finding the Fourth Proportional to 1,145.50, 1,580.78 and 621.55

Step by Step Solution

1. Step 1: Write the proportion equation
   1,145.50 : 1,580.78 = 621.55 : x
2. Step 2: Convert to fraction form
   1,145.50/1,580.78 = 621.55/x
3. Step 3: Cross multiply
   1,145.50x = 1,580.78 × 621.55
4. Step 4: Simplify right side
   1,145.50x = 982,530.70
5. Step 5: Solve for x
   x = 982,530.70/1,145.50
6. Step 6: Final answer
   x = 857.73