Finding the Fourth Proportional to 1,561.20, 2,154.71 and 1,187.58

Step by Step Solution

1. Step 1: Write the proportion equation
   1,561.20 : 2,154.71 = 1,187.58 : x
2. Step 2: Convert to fraction form
   1,561.20/2,154.71 = 1,187.58/x
3. Step 3: Cross multiply
   1,561.20x = 2,154.71 × 1,187.58
4. Step 4: Simplify right side
   1,561.20x = 2,558,884.56
5. Step 5: Solve for x
   x = 2,558,884.56/1,561.20
6. Step 6: Final answer
   x = 1,639.05