Finding the Fourth Proportional to 1,398.63, 2,102.61 and 990.69

Step by Step Solution

1. Step 1: Write the proportion equation
   1,398.63 : 2,102.61 = 990.69 : x
2. Step 2: Convert to fraction form
   1,398.63/2,102.61 = 990.69/x
3. Step 3: Cross multiply
   1,398.63x = 2,102.61 × 990.69
4. Step 4: Simplify right side
   1,398.63x = 2,083,034.70
5. Step 5: Solve for x
   x = 2,083,034.70/1,398.63
6. Step 6: Final answer
   x = 1,489.34