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Finding the Fourth Proportional to 690.80, 1,036.20 and 657.20

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Solution

The fourth proportional to 690.80, 1,036.20 and 657.20 is: 985.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    690.80 : 1,036.20 = 657.20 : x
  2. Step 2: Convert to fraction form
    690.80/1,036.20 = 657.20/x
  3. Step 3: Cross multiply
    690.80x = 1,036.20 × 657.20
  4. Step 4: Simplify right side
    690.80x = 680,990.64
  5. Step 5: Solve for x
    x = 680,990.64/690.80
  6. Step 6: Final answer
    x = 985.80

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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.