Finding the Fourth Proportional to 1,389.88, 1,918.16 and 1,039.96

Step by Step Solution

1. Step 1: Write the proportion equation
   1,389.88 : 1,918.16 = 1,039.96 : x
2. Step 2: Convert to fraction form
   1,389.88/1,918.16 = 1,039.96/x
3. Step 3: Cross multiply
   1,389.88x = 1,918.16 × 1,039.96
4. Step 4: Simplify right side
   1,389.88x = 1,994,809.67
5. Step 5: Solve for x
   x = 1,994,809.67/1,389.88
6. Step 6: Final answer
   x = 1,435.24