Finding the Third Proportional to 865.69 and 1,858.78

Step by Step Solution

1. Step 1: Write the proportion equation
   865.69 : 1,858.78 = 1,858.78 : x
2. Step 2: Convert to fraction form
   865.69/1,858.78 = 1,858.78/x
3. Step 3: Cross multiply
   865.69x = 1,858.78 × 1,858.78
4. Step 4: Simplify right side
   865.69x = 3,455,067.74
5. Step 5: Solve for x
   x = 3,455,067.74/865.69
6. Step 6: Final answer
   x = 3,991.13