Finding the Fourth Proportional to 1,390.31, 1,917.86 and 859.49

Step by Step Solution

1. Step 1: Write the proportion equation
   1,390.31 : 1,917.86 = 859.49 : x
2. Step 2: Convert to fraction form
   1,390.31/1,917.86 = 859.49/x
3. Step 3: Cross multiply
   1,390.31x = 1,917.86 × 859.49
4. Step 4: Simplify right side
   1,390.31x = 1,648,381.99
5. Step 5: Solve for x
   x = 1,648,381.99/1,390.31
6. Step 6: Final answer
   x = 1,185.62