Finding the Fourth Proportional to 2,100.20, 2,898.18 and 1,215.90

Step by Step Solution

1. Step 1: Write the proportion equation
   2,100.20 : 2,898.18 = 1,215.90 : x
2. Step 2: Convert to fraction form
   2,100.20/2,898.18 = 1,215.90/x
3. Step 3: Cross multiply
   2,100.20x = 2,898.18 × 1,215.90
4. Step 4: Simplify right side
   2,100.20x = 3,523,897.06
5. Step 5: Solve for x
   x = 3,523,897.06/2,100.20
6. Step 6: Final answer
   x = 1,677.89