Finding the Fourth Proportional to 1,290.53, 1,781.37 and 870.61

Step by Step Solution

1. Step 1: Write the proportion equation
   1,290.53 : 1,781.37 = 870.61 : x
2. Step 2: Convert to fraction form
   1,290.53/1,781.37 = 870.61/x
3. Step 3: Cross multiply
   1,290.53x = 1,781.37 × 870.61
4. Step 4: Simplify right side
   1,290.53x = 1,550,878.54
5. Step 5: Solve for x
   x = 1,550,878.54/1,290.53
6. Step 6: Final answer
   x = 1,201.74