Finding the Fourth Proportional to 1,387.97, 2,072.02 and 1,286.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,387.97 : 2,072.02 = 1,286.72 : x
2. Step 2: Convert to fraction form
   1,387.97/2,072.02 = 1,286.72/x
3. Step 3: Cross multiply
   1,387.97x = 2,072.02 × 1,286.72
4. Step 4: Simplify right side
   1,387.97x = 2,666,111.54
5. Step 5: Solve for x
   x = 2,666,111.54/1,387.97
6. Step 6: Final answer
   x = 1,920.87