Finding the Fourth Proportional to 1,222.76, 1,687.37 and 663.21

Step by Step Solution

1. Step 1: Write the proportion equation
   1,222.76 : 1,687.37 = 663.21 : x
2. Step 2: Convert to fraction form
   1,222.76/1,687.37 = 663.21/x
3. Step 3: Cross multiply
   1,222.76x = 1,687.37 × 663.21
4. Step 4: Simplify right side
   1,222.76x = 1,119,082.32
5. Step 5: Solve for x
   x = 1,119,082.32/1,222.76
6. Step 6: Final answer
   x = 915.21