Finding the Fourth Proportional to 1,388.51, 1,915.35 and 990.26

Step by Step Solution

1. Step 1: Write the proportion equation
   1,388.51 : 1,915.35 = 990.26 : x
2. Step 2: Convert to fraction form
   1,388.51/1,915.35 = 990.26/x
3. Step 3: Cross multiply
   1,388.51x = 1,915.35 × 990.26
4. Step 4: Simplify right side
   1,388.51x = 1,896,694.49
5. Step 5: Solve for x
   x = 1,896,694.49/1,388.51
6. Step 6: Final answer
   x = 1,365.99