Finding the Fourth Proportional to 1,408.17, 2,115.30 and 860.69

Step by Step Solution

1. Step 1: Write the proportion equation
   1,408.17 : 2,115.30 = 860.69 : x
2. Step 2: Convert to fraction form
   1,408.17/2,115.30 = 860.69/x
3. Step 3: Cross multiply
   1,408.17x = 2,115.30 × 860.69
4. Step 4: Simplify right side
   1,408.17x = 1,820,606.98
5. Step 5: Solve for x
   x = 1,820,606.98/1,408.17
6. Step 6: Final answer
   x = 1,292.89