Finding the Fourth Proportional to 1,288.90, 1,778.69 and 699.43

Step by Step Solution

1. Step 1: Write the proportion equation
   1,288.90 : 1,778.69 = 699.43 : x
2. Step 2: Convert to fraction form
   1,288.90/1,778.69 = 699.43/x
3. Step 3: Cross multiply
   1,288.90x = 1,778.69 × 699.43
4. Step 4: Simplify right side
   1,288.90x = 1,244,061.20
5. Step 5: Solve for x
   x = 1,244,061.20/1,288.90
6. Step 6: Final answer
   x = 965.21