Finding the Fourth Proportional to 1,188.88, 1,640.72 and 664.96

Step by Step Solution

1. Step 1: Write the proportion equation
   1,188.88 : 1,640.72 = 664.96 : x
2. Step 2: Convert to fraction form
   1,188.88/1,640.72 = 664.96/x
3. Step 3: Cross multiply
   1,188.88x = 1,640.72 × 664.96
4. Step 4: Simplify right side
   1,188.88x = 1,091,013.17
5. Step 5: Solve for x
   x = 1,091,013.17/1,188.88
6. Step 6: Final answer
   x = 917.68