Finding the Fourth Proportional to 1,222.01, 1,686.32 and 780.05

Step by Step Solution

1. Step 1: Write the proportion equation
   1,222.01 : 1,686.32 = 780.05 : x
2. Step 2: Convert to fraction form
   1,222.01/1,686.32 = 780.05/x
3. Step 3: Cross multiply
   1,222.01x = 1,686.32 × 780.05
4. Step 4: Simplify right side
   1,222.01x = 1,315,417.16
5. Step 5: Solve for x
   x = 1,315,417.16/1,222.01
6. Step 6: Final answer
   x = 1,076.44