Finding the Fourth Proportional to 1,287.31, 1,776.36 and 790.09

Step by Step Solution

1. Step 1: Write the proportion equation
   1,287.31 : 1,776.36 = 790.09 : x
2. Step 2: Convert to fraction form
   1,287.31/1,776.36 = 790.09/x
3. Step 3: Cross multiply
   1,287.31x = 1,776.36 × 790.09
4. Step 4: Simplify right side
   1,287.31x = 1,403,484.27
5. Step 5: Solve for x
   x = 1,403,484.27/1,287.31
6. Step 6: Final answer
   x = 1,090.25