Finding the Fourth Proportional to 1,290.49, 1,779.89 and 870.18

Step by Step Solution

1. Step 1: Write the proportion equation
   1,290.49 : 1,779.89 = 870.18 : x
2. Step 2: Convert to fraction form
   1,290.49/1,779.89 = 870.18/x
3. Step 3: Cross multiply
   1,290.49x = 1,779.89 × 870.18
4. Step 4: Simplify right side
   1,290.49x = 1,548,813.65
5. Step 5: Solve for x
   x = 1,548,813.65/1,290.49
6. Step 6: Final answer
   x = 1,200.17