Finding the Fourth Proportional to 1,870.40, 2,806.21 and 638.59

Step by Step Solution

1. Step 1: Write the proportion equation
   1,870.40 : 2,806.21 = 638.59 : x
2. Step 2: Convert to fraction form
   1,870.40/2,806.21 = 638.59/x
3. Step 3: Cross multiply
   1,870.40x = 2,806.21 × 638.59
4. Step 4: Simplify right side
   1,870.40x = 1,792,017.64
5. Step 5: Solve for x
   x = 1,792,017.64/1,870.40
6. Step 6: Final answer
   x = 958.09