Finding the Fourth Proportional to 1,389.06, 1,915.20 and 864.18

Step by Step Solution

1. Step 1: Write the proportion equation
   1,389.06 : 1,915.20 = 864.18 : x
2. Step 2: Convert to fraction form
   1,389.06/1,915.20 = 864.18/x
3. Step 3: Cross multiply
   1,389.06x = 1,915.20 × 864.18
4. Step 4: Simplify right side
   1,389.06x = 1,655,077.54
5. Step 5: Solve for x
   x = 1,655,077.54/1,389.06
6. Step 6: Final answer
   x = 1,191.51