Finding the Fourth Proportional to 1,390.89, 1,919.40 and 801.39

Step by Step Solution

1. Step 1: Write the proportion equation
   1,390.89 : 1,919.40 = 801.39 : x
2. Step 2: Convert to fraction form
   1,390.89/1,919.40 = 801.39/x
3. Step 3: Cross multiply
   1,390.89x = 1,919.40 × 801.39
4. Step 4: Simplify right side
   1,390.89x = 1,538,187.97
5. Step 5: Solve for x
   x = 1,538,187.97/1,390.89
6. Step 6: Final answer
   x = 1,105.90