Finding the Fourth Proportional to 1,222.38, 1,687.14 and 780.18

Step by Step Solution

1. Step 1: Write the proportion equation
   1,222.38 : 1,687.14 = 780.18 : x
2. Step 2: Convert to fraction form
   1,222.38/1,687.14 = 780.18/x
3. Step 3: Cross multiply
   1,222.38x = 1,687.14 × 780.18
4. Step 4: Simplify right side
   1,222.38x = 1,316,272.89
5. Step 5: Solve for x
   x = 1,316,272.89/1,222.38
6. Step 6: Final answer
   x = 1,076.81