Finding the Fourth Proportional to 1,390.98, 1,919.76 and 860.16

Step by Step Solution

1. Step 1: Write the proportion equation
   1,390.98 : 1,919.76 = 860.16 : x
2. Step 2: Convert to fraction form
   1,390.98/1,919.76 = 860.16/x
3. Step 3: Cross multiply
   1,390.98x = 1,919.76 × 860.16
4. Step 4: Simplify right side
   1,390.98x = 1,651,300.76
5. Step 5: Solve for x
   x = 1,651,300.76/1,390.98
6. Step 6: Final answer
   x = 1,187.15