Finding the Fourth Proportional to 1,389.89, 1,918.55 and 830.55

Step by Step Solution

1. Step 1: Write the proportion equation
   1,389.89 : 1,918.55 = 830.55 : x
2. Step 2: Convert to fraction form
   1,389.89/1,918.55 = 830.55/x
3. Step 3: Cross multiply
   1,389.89x = 1,918.55 × 830.55
4. Step 4: Simplify right side
   1,389.89x = 1,593,460.97
5. Step 5: Solve for x
   x = 1,593,460.97/1,389.89
6. Step 6: Final answer
   x = 1,146.46