Finding the Fourth Proportional to 1,187.38, 1,638.61 and 663.41

Step by Step Solution

1. Step 1: Write the proportion equation
   1,187.38 : 1,638.61 = 663.41 : x
2. Step 2: Convert to fraction form
   1,187.38/1,638.61 = 663.41/x
3. Step 3: Cross multiply
   1,187.38x = 1,638.61 × 663.41
4. Step 4: Simplify right side
   1,187.38x = 1,087,067.21
5. Step 5: Solve for x
   x = 1,087,067.21/1,187.38
6. Step 6: Final answer
   x = 915.52