Finding the Fourth Proportional to 1,166.72, 1,609.92 and 642.78

Step by Step Solution

1. Step 1: Write the proportion equation
   1,166.72 : 1,609.92 = 642.78 : x
2. Step 2: Convert to fraction form
   1,166.72/1,609.92 = 642.78/x
3. Step 3: Cross multiply
   1,166.72x = 1,609.92 × 642.78
4. Step 4: Simplify right side
   1,166.72x = 1,034,824.38
5. Step 5: Solve for x
   x = 1,034,824.38/1,166.72
6. Step 6: Final answer
   x = 886.96