Finding the Fourth Proportional to 2,166.28, 2,988.72 and 1,221.95

Step by Step Solution

1. Step 1: Write the proportion equation
   2,166.28 : 2,988.72 = 1,221.95 : x
2. Step 2: Convert to fraction form
   2,166.28/2,988.72 = 1,221.95/x
3. Step 3: Cross multiply
   2,166.28x = 2,988.72 × 1,221.95
4. Step 4: Simplify right side
   2,166.28x = 3,652,073.88
5. Step 5: Solve for x
   x = 3,652,073.88/2,166.28
6. Step 6: Final answer
   x = 1,685.88