Finding the Fourth Proportional to 1,187.86, 1,639.27 and 663.89

Step by Step Solution

1. Step 1: Write the proportion equation
   1,187.86 : 1,639.27 = 663.89 : x
2. Step 2: Convert to fraction form
   1,187.86/1,639.27 = 663.89/x
3. Step 3: Cross multiply
   1,187.86x = 1,639.27 × 663.89
4. Step 4: Simplify right side
   1,187.86x = 1,088,294.96
5. Step 5: Solve for x
   x = 1,088,294.96/1,187.86
6. Step 6: Final answer
   x = 916.18