Finding the Fourth Proportional to 1,542.78, 2,128.51 and 879.15

Step by Step Solution

1. Step 1: Write the proportion equation
   1,542.78 : 2,128.51 = 879.15 : x
2. Step 2: Convert to fraction form
   1,542.78/2,128.51 = 879.15/x
3. Step 3: Cross multiply
   1,542.78x = 2,128.51 × 879.15
4. Step 4: Simplify right side
   1,542.78x = 1,871,282.69
5. Step 5: Solve for x
   x = 1,871,282.69/1,542.78
6. Step 6: Final answer
   x = 1,212.93