Finding the Fourth Proportional to 2,172.47, 2,998.40 and 1,288.71

Step by Step Solution

1. Step 1: Write the proportion equation
   2,172.47 : 2,998.40 = 1,288.71 : x
2. Step 2: Convert to fraction form
   2,172.47/2,998.40 = 1,288.71/x
3. Step 3: Cross multiply
   2,172.47x = 2,998.40 × 1,288.71
4. Step 4: Simplify right side
   2,172.47x = 3,864,061.62
5. Step 5: Solve for x
   x = 3,864,061.62/2,172.47
6. Step 6: Final answer
   x = 1,778.65