Finding the Fourth Proportional to 1,380.63, 2,071.61 and 860.50

Step by Step Solution

1. Step 1: Write the proportion equation
   1,380.63 : 2,071.61 = 860.50 : x
2. Step 2: Convert to fraction form
   1,380.63/2,071.61 = 860.50/x
3. Step 3: Cross multiply
   1,380.63x = 2,071.61 × 860.50
4. Step 4: Simplify right side
   1,380.63x = 1,782,620.41
5. Step 5: Solve for x
   x = 1,782,620.41/1,380.63
6. Step 6: Final answer
   x = 1,291.16