Finding the Fourth Proportional to 1,370.72, 2,054.72 and 639.68

Step by Step Solution

1. Step 1: Write the proportion equation
   1,370.72 : 2,054.72 = 639.68 : x
2. Step 2: Convert to fraction form
   1,370.72/2,054.72 = 639.68/x
3. Step 3: Cross multiply
   1,370.72x = 2,054.72 × 639.68
4. Step 4: Simplify right side
   1,370.72x = 1,314,363.29
5. Step 5: Solve for x
   x = 1,314,363.29/1,370.72
6. Step 6: Final answer
   x = 958.89