Finding the Fourth Proportional to 1,380.57, 1,905.62 and 1,223.75

Step by Step Solution

1. Step 1: Write the proportion equation
   1,380.57 : 1,905.62 = 1,223.75 : x
2. Step 2: Convert to fraction form
   1,380.57/1,905.62 = 1,223.75/x
3. Step 3: Cross multiply
   1,380.57x = 1,905.62 × 1,223.75
4. Step 4: Simplify right side
   1,380.57x = 2,331,986.83
5. Step 5: Solve for x
   x = 2,331,986.83/1,380.57
6. Step 6: Final answer
   x = 1,689.15