Finding the Fourth Proportional to 1,986.07, 2,978.16 and 815.89

Step by Step Solution

1. Step 1: Write the proportion equation
   1,986.07 : 2,978.16 = 815.89 : x
2. Step 2: Convert to fraction form
   1,986.07/2,978.16 = 815.89/x
3. Step 3: Cross multiply
   1,986.07x = 2,978.16 × 815.89
4. Step 4: Simplify right side
   1,986.07x = 2,429,850.96
5. Step 5: Solve for x
   x = 2,429,850.96/1,986.07
6. Step 6: Final answer
   x = 1,223.45