Finding the Fourth Proportional to 1,389.95, 1,918.35 and 830.86

Step by Step Solution

1. Step 1: Write the proportion equation
   1,389.95 : 1,918.35 = 830.86 : x
2. Step 2: Convert to fraction form
   1,389.95/1,918.35 = 830.86/x
3. Step 3: Cross multiply
   1,389.95x = 1,918.35 × 830.86
4. Step 4: Simplify right side
   1,389.95x = 1,593,870.69
5. Step 5: Solve for x
   x = 1,593,870.69/1,389.95
6. Step 6: Final answer
   x = 1,146.71