Finding the Fourth Proportional to 1,216.89, 1,821.42 and 667.71

Step by Step Solution

1. Step 1: Write the proportion equation
   1,216.89 : 1,821.42 = 667.71 : x
2. Step 2: Convert to fraction form
   1,216.89/1,821.42 = 667.71/x
3. Step 3: Cross multiply
   1,216.89x = 1,821.42 × 667.71
4. Step 4: Simplify right side
   1,216.89x = 1,216,180.35
5. Step 5: Solve for x
   x = 1,216,180.35/1,216.89
6. Step 6: Final answer
   x = 999.42