Finding the Fourth Proportional to 1,389.43, 1,915.95 and 864.55

Step by Step Solution

1. Step 1: Write the proportion equation
   1,389.43 : 1,915.95 = 864.55 : x
2. Step 2: Convert to fraction form
   1,389.43/1,915.95 = 864.55/x
3. Step 3: Cross multiply
   1,389.43x = 1,915.95 × 864.55
4. Step 4: Simplify right side
   1,389.43x = 1,656,434.57
5. Step 5: Solve for x
   x = 1,656,434.57/1,389.43
6. Step 6: Final answer
   x = 1,192.17