Finding the Fourth Proportional to 1,390.27, 1,918.28 and 830.53

Step by Step Solution

1. Step 1: Write the proportion equation
   1,390.27 : 1,918.28 = 830.53 : x
2. Step 2: Convert to fraction form
   1,390.27/1,918.28 = 830.53/x
3. Step 3: Cross multiply
   1,390.27x = 1,918.28 × 830.53
4. Step 4: Simplify right side
   1,390.27x = 1,593,189.09
5. Step 5: Solve for x
   x = 1,593,189.09/1,390.27
6. Step 6: Final answer
   x = 1,145.96