Finding the Fourth Proportional to 1,187.59, 1,638.83 and 663.61

Step by Step Solution

1. Step 1: Write the proportion equation
   1,187.59 : 1,638.83 = 663.61 : x
2. Step 2: Convert to fraction form
   1,187.59/1,638.83 = 663.61/x
3. Step 3: Cross multiply
   1,187.59x = 1,638.83 × 663.61
4. Step 4: Simplify right side
   1,187.59x = 1,087,532.46
5. Step 5: Solve for x
   x = 1,087,532.46/1,187.59
6. Step 6: Final answer
   x = 915.75