Finding the Fourth Proportional to 1,223.39, 1,688.28 and 663.86

Step by Step Solution

1. Step 1: Write the proportion equation
   1,223.39 : 1,688.28 = 663.86 : x
2. Step 2: Convert to fraction form
   1,223.39/1,688.28 = 663.86/x
3. Step 3: Cross multiply
   1,223.39x = 1,688.28 × 663.86
4. Step 4: Simplify right side
   1,223.39x = 1,120,773.12
5. Step 5: Solve for x
   x = 1,120,773.12/1,223.39
6. Step 6: Final answer
   x = 916.12