Finding the Fourth Proportional to 1,188.38, 1,639.86 and 664.31

Step by Step Solution

1. Step 1: Write the proportion equation
   1,188.38 : 1,639.86 = 664.31 : x
2. Step 2: Convert to fraction form
   1,188.38/1,639.86 = 664.31/x
3. Step 3: Cross multiply
   1,188.38x = 1,639.86 × 664.31
4. Step 4: Simplify right side
   1,188.38x = 1,089,375.40
5. Step 5: Solve for x
   x = 1,089,375.40/1,188.38
6. Step 6: Final answer
   x = 916.69