Finding the Fourth Proportional to 3,913.45, 5,870.37 and 991.78

Step by Step Solution

1. Step 1: Write the proportion equation
   3,913.45 : 5,870.37 = 991.78 : x
2. Step 2: Convert to fraction form
   3,913.45/5,870.37 = 991.78/x
3. Step 3: Cross multiply
   3,913.45x = 5,870.37 × 991.78
4. Step 4: Simplify right side
   3,913.45x = 5,822,104.60
5. Step 5: Solve for x
   x = 5,822,104.60/3,913.45
6. Step 6: Final answer
   x = 1,487.72