Finding the Fourth Proportional to 2,613.71, 3,920.78 and 665.91

Step by Step Solution

1. Step 1: Write the proportion equation
   2,613.71 : 3,920.78 = 665.91 : x
2. Step 2: Convert to fraction form
   2,613.71/3,920.78 = 665.91/x
3. Step 3: Cross multiply
   2,613.71x = 3,920.78 × 665.91
4. Step 4: Simplify right side
   2,613.71x = 2,610,888.27
5. Step 5: Solve for x
   x = 2,610,888.27/2,613.71
6. Step 6: Final answer
   x = 998.92