Finding the Fourth Proportional to 2,215.10, 3,321.45 and 915.10

Step by Step Solution

1. Step 1: Write the proportion equation
   2,215.10 : 3,321.45 = 915.10 : x
2. Step 2: Convert to fraction form
   2,215.10/3,321.45 = 915.10/x
3. Step 3: Cross multiply
   2,215.10x = 3,321.45 × 915.10
4. Step 4: Simplify right side
   2,215.10x = 3,039,458.90
5. Step 5: Solve for x
   x = 3,039,458.90/2,215.10
6. Step 6: Final answer
   x = 1,372.15