Finding the Fourth Proportional to 1,209.05, 1,668.72 and 789.76

Step by Step Solution

1. Step 1: Write the proportion equation
   1,209.05 : 1,668.72 = 789.76 : x
2. Step 2: Convert to fraction form
   1,209.05/1,668.72 = 789.76/x
3. Step 3: Cross multiply
   1,209.05x = 1,668.72 × 789.76
4. Step 4: Simplify right side
   1,209.05x = 1,317,884.22
5. Step 5: Solve for x
   x = 1,317,884.22/1,209.05
6. Step 6: Final answer
   x = 1,090.01