Finding the Fourth Proportional to 1,605.21, 2,215.40 and 906.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,605.21 : 2,215.40 = 906.72 : x
2. Step 2: Convert to fraction form
   1,605.21/2,215.40 = 906.72/x
3. Step 3: Cross multiply
   1,605.21x = 2,215.40 × 906.72
4. Step 4: Simplify right side
   1,605.21x = 2,008,742.95
5. Step 5: Solve for x
   x = 2,008,742.95/1,605.21
6. Step 6: Final answer
   x = 1,251.39