Finding the Fourth Proportional to 1,189.57, 1,641.69 and 665.71

Step by Step Solution

1. Step 1: Write the proportion equation
   1,189.57 : 1,641.69 = 665.71 : x
2. Step 2: Convert to fraction form
   1,189.57/1,641.69 = 665.71/x
3. Step 3: Cross multiply
   1,189.57x = 1,641.69 × 665.71
4. Step 4: Simplify right side
   1,189.57x = 1,092,889.45
5. Step 5: Solve for x
   x = 1,092,889.45/1,189.57
6. Step 6: Final answer
   x = 918.73