Finding the Fourth Proportional to 2,165.31, 2,988.18 and 1,221.30

Step by Step Solution

1. Step 1: Write the proportion equation
   2,165.31 : 2,988.18 = 1,221.30 : x
2. Step 2: Convert to fraction form
   2,165.31/2,988.18 = 1,221.30/x
3. Step 3: Cross multiply
   2,165.31x = 2,988.18 × 1,221.30
4. Step 4: Simplify right side
   2,165.31x = 3,649,464.23
5. Step 5: Solve for x
   x = 3,649,464.23/2,165.31
6. Step 6: Final answer
   x = 1,685.42