Finding the Fourth Proportional to 1,386.72, 1,913.94 and 989.46

Step by Step Solution

1. Step 1: Write the proportion equation
   1,386.72 : 1,913.94 = 989.46 : x
2. Step 2: Convert to fraction form
   1,386.72/1,913.94 = 989.46/x
3. Step 3: Cross multiply
   1,386.72x = 1,913.94 × 989.46
4. Step 4: Simplify right side
   1,386.72x = 1,893,767.07
5. Step 5: Solve for x
   x = 1,893,767.07/1,386.72
6. Step 6: Final answer
   x = 1,365.64