Finding the Fourth Proportional to 2,116.50, 2,920.77 and 1,288.50

Step by Step Solution

1. Step 1: Write the proportion equation
   2,116.50 : 2,920.77 = 1,288.50 : x
2. Step 2: Convert to fraction form
   2,116.50/2,920.77 = 1,288.50/x
3. Step 3: Cross multiply
   2,116.50x = 2,920.77 × 1,288.50
4. Step 4: Simplify right side
   2,116.50x = 3,763,412.15
5. Step 5: Solve for x
   x = 3,763,412.15/2,116.50
6. Step 6: Final answer
   x = 1,778.13