Finding the Fourth Proportional to 1,561.61, 2,155.05 and 853.47

Step by Step Solution

1. Step 1: Write the proportion equation
   1,561.61 : 2,155.05 = 853.47 : x
2. Step 2: Convert to fraction form
   1,561.61/2,155.05 = 853.47/x
3. Step 3: Cross multiply
   1,561.61x = 2,155.05 × 853.47
4. Step 4: Simplify right side
   1,561.61x = 1,839,255.48
5. Step 5: Solve for x
   x = 1,839,255.48/1,561.61
6. Step 6: Final answer
   x = 1,177.79