Finding the Fourth Proportional to 1,387.74, 1,915.25 and 891.57

Step by Step Solution

1. Step 1: Write the proportion equation
   1,387.74 : 1,915.25 = 891.57 : x
2. Step 2: Convert to fraction form
   1,387.74/1,915.25 = 891.57/x
3. Step 3: Cross multiply
   1,387.74x = 1,915.25 × 891.57
4. Step 4: Simplify right side
   1,387.74x = 1,707,574.98
5. Step 5: Solve for x
   x = 1,707,574.98/1,387.74
6. Step 6: Final answer
   x = 1,230.47