Finding the Fourth Proportional to 2,147.31, 3,221.43 and 666.50

Step by Step Solution

1. Step 1: Write the proportion equation
   2,147.31 : 3,221.43 = 666.50 : x
2. Step 2: Convert to fraction form
   2,147.31/3,221.43 = 666.50/x
3. Step 3: Cross multiply
   2,147.31x = 3,221.43 × 666.50
4. Step 4: Simplify right side
   2,147.31x = 2,147,085.63
5. Step 5: Solve for x
   x = 2,147,085.63/2,147.31
6. Step 6: Final answer
   x = 999.90