Finding the Fourth Proportional to 1,288.86, 1,919.69 and 1,261.86

Step by Step Solution

1. Step 1: Write the proportion equation
   1,288.86 : 1,919.69 = 1,261.86 : x
2. Step 2: Convert to fraction form
   1,288.86/1,919.69 = 1,261.86/x
3. Step 3: Cross multiply
   1,288.86x = 1,919.69 × 1,261.86
4. Step 4: Simplify right side
   1,288.86x = 2,422,380.02
5. Step 5: Solve for x
   x = 2,422,380.02/1,288.86
6. Step 6: Final answer
   x = 1,879.47