Finding the Fourth Proportional to 1,166.09, 1,609.20 and 642.15

Step by Step Solution

1. Step 1: Write the proportion equation
   1,166.09 : 1,609.20 = 642.15 : x
2. Step 2: Convert to fraction form
   1,166.09/1,609.20 = 642.15/x
3. Step 3: Cross multiply
   1,166.09x = 1,609.20 × 642.15
4. Step 4: Simplify right side
   1,166.09x = 1,033,347.78
5. Step 5: Solve for x
   x = 1,033,347.78/1,166.09
6. Step 6: Final answer
   x = 886.17