Finding the Fourth Proportional to 1,222.65, 1,687.20 and 691.55

Step by Step Solution

1. Step 1: Write the proportion equation
   1,222.65 : 1,687.20 = 691.55 : x
2. Step 2: Convert to fraction form
   1,222.65/1,687.20 = 691.55/x
3. Step 3: Cross multiply
   1,222.65x = 1,687.20 × 691.55
4. Step 4: Simplify right side
   1,222.65x = 1,166,774.72
5. Step 5: Solve for x
   x = 1,166,774.72/1,222.65
6. Step 6: Final answer
   x = 954.30