Finding the Fourth Proportional to 1,535.72, 2,119.80 and 1,221.56

Step by Step Solution

1. Step 1: Write the proportion equation
   1,535.72 : 2,119.80 = 1,221.56 : x
2. Step 2: Convert to fraction form
   1,535.72/2,119.80 = 1,221.56/x
3. Step 3: Cross multiply
   1,535.72x = 2,119.80 × 1,221.56
4. Step 4: Simplify right side
   1,535.72x = 2,589,462.89
5. Step 5: Solve for x
   x = 2,589,462.89/1,535.72
6. Step 6: Final answer
   x = 1,686.16