Finding the Fourth Proportional to 1,561.86, 2,155.39 and 853.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,561.86 : 2,155.39 = 853.72 : x
2. Step 2: Convert to fraction form
   1,561.86/2,155.39 = 853.72/x
3. Step 3: Cross multiply
   1,561.86x = 2,155.39 × 853.72
4. Step 4: Simplify right side
   1,561.86x = 1,840,088.77
5. Step 5: Solve for x
   x = 1,840,088.77/1,561.86
6. Step 6: Final answer
   x = 1,178.14