Finding the Third Proportional to 1,040 and 1,390

Step by Step Solution

1. Step 1: Write the proportion equation
   1,040 : 1,390 = 1,390 : x
2. Step 2: Convert to fraction form
   1,040/1,390 = 1,390/x
3. Step 3: Cross multiply
   1,040x = 1,390 × 1,390
4. Step 4: Simplify right side
   1,040x = 1,932,100
5. Step 5: Solve for x
   x = 1,932,100/1,040
6. Step 6: Final answer
   x = 1,857.79