Finding the Fourth Proportional to 1,287.63, 1,780.38 and 1,228.50

Step by Step Solution

1. Step 1: Write the proportion equation
   1,287.63 : 1,780.38 = 1,228.50 : x
2. Step 2: Convert to fraction form
   1,287.63/1,780.38 = 1,228.50/x
3. Step 3: Cross multiply
   1,287.63x = 1,780.38 × 1,228.50
4. Step 4: Simplify right side
   1,287.63x = 2,187,196.83
5. Step 5: Solve for x
   x = 2,187,196.83/1,287.63
6. Step 6: Final answer
   x = 1,698.62