Finding the Fourth Proportional to 1,387.65, 1,914.78 and 790.23

Step by Step Solution

1. Step 1: Write the proportion equation
   1,387.65 : 1,914.78 = 790.23 : x
2. Step 2: Convert to fraction form
   1,387.65/1,914.78 = 790.23/x
3. Step 3: Cross multiply
   1,387.65x = 1,914.78 × 790.23
4. Step 4: Simplify right side
   1,387.65x = 1,513,109.00
5. Step 5: Solve for x
   x = 1,513,109.00/1,387.65
6. Step 6: Final answer
   x = 1,090.41