Finding the Fourth Proportional to 1,188.50, 1,640.12 and 664.56

Step by Step Solution

1. Step 1: Write the proportion equation
   1,188.50 : 1,640.12 = 664.56 : x
2. Step 2: Convert to fraction form
   1,188.50/1,640.12 = 664.56/x
3. Step 3: Cross multiply
   1,188.50x = 1,640.12 × 664.56
4. Step 4: Simplify right side
   1,188.50x = 1,089,954.82
5. Step 5: Solve for x
   x = 1,089,954.82/1,188.50
6. Step 6: Final answer
   x = 917.09