Finding the Fourth Proportional to 1,188.81, 1,640.72 and 664.88

Step by Step Solution

1. Step 1: Write the proportion equation
   1,188.81 : 1,640.72 = 664.88 : x
2. Step 2: Convert to fraction form
   1,188.81/1,640.72 = 664.88/x
3. Step 3: Cross multiply
   1,188.81x = 1,640.72 × 664.88
4. Step 4: Simplify right side
   1,188.81x = 1,090,875.37
5. Step 5: Solve for x
   x = 1,090,875.37/1,188.81
6. Step 6: Final answer
   x = 917.62