Finding the Fourth Proportional to 1,086.45, 1,635.55 and 989.57

Step by Step Solution

1. Step 1: Write the proportion equation
   1,086.45 : 1,635.55 = 989.57 : x
2. Step 2: Convert to fraction form
   1,086.45/1,635.55 = 989.57/x
3. Step 3: Cross multiply
   1,086.45x = 1,635.55 × 989.57
4. Step 4: Simplify right side
   1,086.45x = 1,618,500.39
5. Step 5: Solve for x
   x = 1,618,500.39/1,086.45
6. Step 6: Final answer
   x = 1,489.71