Finding the Fourth Proportional to 1,389.65, 1,917.40 and 830.30

Step by Step Solution

1. Step 1: Write the proportion equation
   1,389.65 : 1,917.40 = 830.30 : x
2. Step 2: Convert to fraction form
   1,389.65/1,917.40 = 830.30/x
3. Step 3: Cross multiply
   1,389.65x = 1,917.40 × 830.30
4. Step 4: Simplify right side
   1,389.65x = 1,592,019.94
5. Step 5: Solve for x
   x = 1,592,019.94/1,389.65
6. Step 6: Final answer
   x = 1,145.62