Finding the Fourth Proportional to 2,172.56, 2,997.61 and 1,288.20

Step by Step Solution

1. Step 1: Write the proportion equation
   2,172.56 : 2,997.61 = 1,288.20 : x
2. Step 2: Convert to fraction form
   2,172.56/2,997.61 = 1,288.20/x
3. Step 3: Cross multiply
   2,172.56x = 2,997.61 × 1,288.20
4. Step 4: Simplify right side
   2,172.56x = 3,861,529.22
5. Step 5: Solve for x
   x = 3,861,529.22/2,172.56
6. Step 6: Final answer
   x = 1,777.41