Finding the Fourth Proportional to 1,443.20, 1,991.36 and 853.76

Step by Step Solution

1. Step 1: Write the proportion equation
   1,443.20 : 1,991.36 = 853.76 : x
2. Step 2: Convert to fraction form
   1,443.20/1,991.36 = 853.76/x
3. Step 3: Cross multiply
   1,443.20x = 1,991.36 × 853.76
4. Step 4: Simplify right side
   1,443.20x = 1,700,143.51
5. Step 5: Solve for x
   x = 1,700,143.51/1,443.20
6. Step 6: Final answer
   x = 1,178.04