Finding the Fourth Proportional to 1,321.12, 1,822.72 and 789.76

Step by Step Solution

1. Step 1: Write the proportion equation
   1,321.12 : 1,822.72 = 789.76 : x
2. Step 2: Convert to fraction form
   1,321.12/1,822.72 = 789.76/x
3. Step 3: Cross multiply
   1,321.12x = 1,822.72 × 789.76
4. Step 4: Simplify right side
   1,321.12x = 1,439,511.35
5. Step 5: Solve for x
   x = 1,439,511.35/1,321.12
6. Step 6: Final answer
   x = 1,089.61