Finding the Fourth Proportional to 1,373.78, 2,061.34 and 643.22

Step by Step Solution

1. Step 1: Write the proportion equation
   1,373.78 : 2,061.34 = 643.22 : x
2. Step 2: Convert to fraction form
   1,373.78/2,061.34 = 643.22/x
3. Step 3: Cross multiply
   1,373.78x = 2,061.34 × 643.22
4. Step 4: Simplify right side
   1,373.78x = 1,325,895.11
5. Step 5: Solve for x
   x = 1,325,895.11/1,373.78
6. Step 6: Final answer
   x = 965.14