Finding the Fourth Proportional to 1,380.29, 2,071.25 and 989.87

Step by Step Solution

1. Step 1: Write the proportion equation
   1,380.29 : 2,071.25 = 989.87 : x
2. Step 2: Convert to fraction form
   1,380.29/2,071.25 = 989.87/x
3. Step 3: Cross multiply
   1,380.29x = 2,071.25 × 989.87
4. Step 4: Simplify right side
   1,380.29x = 2,050,263.29
5. Step 5: Solve for x
   x = 2,050,263.29/1,380.29
6. Step 6: Final answer
   x = 1,485.39