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Finding the Fourth Proportional to 857.64, 1,287.18 and 687.72

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Solution

The fourth proportional to 857.64, 1,287.18 and 687.72 is: 1,032.16

Step by Step Solution

  1. Step 1: Write the proportion equation
    857.64 : 1,287.18 = 687.72 : x
  2. Step 2: Convert to fraction form
    857.64/1,287.18 = 687.72/x
  3. Step 3: Cross multiply
    857.64x = 1,287.18 × 687.72
  4. Step 4: Simplify right side
    857.64x = 885,219.43
  5. Step 5: Solve for x
    x = 885,219.43/857.64
  6. Step 6: Final answer
    x = 1,032.16

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.