Finding the Fourth Proportional to 1,461.09, 2,189.78 and 639.15

Step by Step Solution

1. Step 1: Write the proportion equation
   1,461.09 : 2,189.78 = 639.15 : x
2. Step 2: Convert to fraction form
   1,461.09/2,189.78 = 639.15/x
3. Step 3: Cross multiply
   1,461.09x = 2,189.78 × 639.15
4. Step 4: Simplify right side
   1,461.09x = 1,399,597.89
5. Step 5: Solve for x
   x = 1,399,597.89/1,461.09
6. Step 6: Final answer
   x = 957.91