Finding the Fourth Proportional to 1,188.52, 1,640.18 and 664.55

Step by Step Solution

1. Step 1: Write the proportion equation
   1,188.52 : 1,640.18 = 664.55 : x
2. Step 2: Convert to fraction form
   1,188.52/1,640.18 = 664.55/x
3. Step 3: Cross multiply
   1,188.52x = 1,640.18 × 664.55
4. Step 4: Simplify right side
   1,188.52x = 1,089,981.62
5. Step 5: Solve for x
   x = 1,089,981.62/1,188.52
6. Step 6: Final answer
   x = 917.09