Finding the Fourth Proportional to 1,978.20, 2,729.06 and 1,389.12

Step by Step Solution

1. Step 1: Write the proportion equation
   1,978.20 : 2,729.06 = 1,389.12 : x
2. Step 2: Convert to fraction form
   1,978.20/2,729.06 = 1,389.12/x
3. Step 3: Cross multiply
   1,978.20x = 2,729.06 × 1,389.12
4. Step 4: Simplify right side
   1,978.20x = 3,790,991.83
5. Step 5: Solve for x
   x = 3,790,991.83/1,978.20
6. Step 6: Final answer
   x = 1,916.38