Finding the Fourth Proportional to 1,389.42, 2,086.38 and 879.66

Step by Step Solution

1. Step 1: Write the proportion equation
   1,389.42 : 2,086.38 = 879.66 : x
2. Step 2: Convert to fraction form
   1,389.42/2,086.38 = 879.66/x
3. Step 3: Cross multiply
   1,389.42x = 2,086.38 × 879.66
4. Step 4: Simplify right side
   1,389.42x = 1,835,305.03
5. Step 5: Solve for x
   x = 1,835,305.03/1,389.42
6. Step 6: Final answer
   x = 1,320.91