Finding the Fourth Proportional to 2,019.72, 2,787.90 and 1,389.72

Step by Step Solution

1. Step 1: Write the proportion equation
   2,019.72 : 2,787.90 = 1,389.72 : x
2. Step 2: Convert to fraction form
   2,019.72/2,787.90 = 1,389.72/x
3. Step 3: Cross multiply
   2,019.72x = 2,787.90 × 1,389.72
4. Step 4: Simplify right side
   2,019.72x = 3,874,400.39
5. Step 5: Solve for x
   x = 3,874,400.39/2,019.72
6. Step 6: Final answer
   x = 1,918.29