Finding the Fourth Proportional to 1,393.71, 1,906.82 and 1,387.91

Step by Step Solution

1. Step 1: Write the proportion equation
   1,393.71 : 1,906.82 = 1,387.91 : x
2. Step 2: Convert to fraction form
   1,393.71/1,906.82 = 1,387.91/x
3. Step 3: Cross multiply
   1,393.71x = 1,906.82 × 1,387.91
4. Step 4: Simplify right side
   1,393.71x = 2,646,478.07
5. Step 5: Solve for x
   x = 2,646,478.07/1,393.71
6. Step 6: Final answer
   x = 1,898.87