Finding the Fourth Proportional to 1,085.13, 1,496.61 and 642.60

Step by Step Solution

1. Step 1: Write the proportion equation
   1,085.13 : 1,496.61 = 642.60 : x
2. Step 2: Convert to fraction form
   1,085.13/1,496.61 = 642.60/x
3. Step 3: Cross multiply
   1,085.13x = 1,496.61 × 642.60
4. Step 4: Simplify right side
   1,085.13x = 961,721.59
5. Step 5: Solve for x
   x = 961,721.59/1,085.13
6. Step 6: Final answer
   x = 886.27