Finding the Fourth Proportional to 1,077.72, 1,616.51 and 428.00

Step by Step Solution

1. Step 1: Write the proportion equation
   1,077.72 : 1,616.51 = 428.00 : x
2. Step 2: Convert to fraction form
   1,077.72/1,616.51 = 428.00/x
3. Step 3: Cross multiply
   1,077.72x = 1,616.51 × 428.00
4. Step 4: Simplify right side
   1,077.72x = 691,856.06
5. Step 5: Solve for x
   x = 691,856.06/1,077.72
6. Step 6: Final answer
   x = 641.96