Finding the Third Proportional to 697.78 and 1,664.72

Step by Step Solution

1. Step 1: Write the proportion equation
   697.78 : 1,664.72 = 1,664.72 : x
2. Step 2: Convert to fraction form
   697.78/1,664.72 = 1,664.72/x
3. Step 3: Cross multiply
   697.78x = 1,664.72 × 1,664.72
4. Step 4: Simplify right side
   697.78x = 2,771,288.52
5. Step 5: Solve for x
   x = 2,771,288.52/697.78
6. Step 6: Final answer
   x = 3,971.57