Finding the Fourth Proportional to 1,478.79, 2,216.70 and 990.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,478.79 : 2,216.70 = 990.72 : x
2. Step 2: Convert to fraction form
   1,478.79/2,216.70 = 990.72/x
3. Step 3: Cross multiply
   1,478.79x = 2,216.70 × 990.72
4. Step 4: Simplify right side
   1,478.79x = 2,196,129.02
5. Step 5: Solve for x
   x = 2,196,129.02/1,478.79
6. Step 6: Final answer
   x = 1,485.09