Finding the Fourth Proportional to 1,221.85, 1,686.15 and 662.31

Step by Step Solution

1. Step 1: Write the proportion equation
   1,221.85 : 1,686.15 = 662.31 : x
2. Step 2: Convert to fraction form
   1,221.85/1,686.15 = 662.31/x
3. Step 3: Cross multiply
   1,221.85x = 1,686.15 × 662.31
4. Step 4: Simplify right side
   1,221.85x = 1,116,754.01
5. Step 5: Solve for x
   x = 1,116,754.01/1,221.85
6. Step 6: Final answer
   x = 913.99