Finding the Fourth Proportional to 2,840.72, 4,259.70 and 991.78

Step by Step Solution

1. Step 1: Write the proportion equation
   2,840.72 : 4,259.70 = 991.78 : x
2. Step 2: Convert to fraction form
   2,840.72/4,259.70 = 991.78/x
3. Step 3: Cross multiply
   2,840.72x = 4,259.70 × 991.78
4. Step 4: Simplify right side
   2,840.72x = 4,224,685.27
5. Step 5: Solve for x
   x = 4,224,685.27/2,840.72
6. Step 6: Final answer
   x = 1,487.19