Finding the Fourth Proportional to 1,222.84, 1,687.72 and 780.96

Step by Step Solution

1. Step 1: Write the proportion equation
   1,222.84 : 1,687.72 = 780.96 : x
2. Step 2: Convert to fraction form
   1,222.84/1,687.72 = 780.96/x
3. Step 3: Cross multiply
   1,222.84x = 1,687.72 × 780.96
4. Step 4: Simplify right side
   1,222.84x = 1,318,041.81
5. Step 5: Solve for x
   x = 1,318,041.81/1,222.84
6. Step 6: Final answer
   x = 1,077.85