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Finding the Fourth Proportional to 1,398.40, 1,929.76 and 777.40

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Solution

The fourth proportional to 1,398.40, 1,929.76 and 777.40 is: 1,072.79

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,398.40 : 1,929.76 = 777.40 : x
  2. Step 2: Convert to fraction form
    1,398.40/1,929.76 = 777.40/x
  3. Step 3: Cross multiply
    1,398.40x = 1,929.76 × 777.40
  4. Step 4: Simplify right side
    1,398.40x = 1,500,195.42
  5. Step 5: Solve for x
    x = 1,500,195.42/1,398.40
  6. Step 6: Final answer
    x = 1,072.79

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.