Finding the Fourth Proportional to 1,389.39, 2,083.86 and 512.31

Step by Step Solution

1. Step 1: Write the proportion equation
   1,389.39 : 2,083.86 = 512.31 : x
2. Step 2: Convert to fraction form
   1,389.39/2,083.86 = 512.31/x
3. Step 3: Cross multiply
   1,389.39x = 2,083.86 × 512.31
4. Step 4: Simplify right side
   1,389.39x = 1,067,581.96
5. Step 5: Solve for x
   x = 1,067,581.96/1,389.39
6. Step 6: Final answer
   x = 768.38