Finding the Third Proportional to 378.56 and 780.56

Step by Step Solution

1. Step 1: Write the proportion equation
   378.56 : 780.56 = 780.56 : x
2. Step 2: Convert to fraction form
   378.56/780.56 = 780.56/x
3. Step 3: Cross multiply
   378.56x = 780.56 × 780.56
4. Step 4: Simplify right side
   378.56x = 609,277.82
5. Step 5: Solve for x
   x = 609,277.82/378.56
6. Step 6: Final answer
   x = 1,609.45