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Finding the Fourth Proportional to 1,215.96, 1,678.20 and 920.70

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Solution

The fourth proportional to 1,215.96, 1,678.20 and 920.70 is: 1,270.70

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,215.96 : 1,678.20 = 920.70 : x
  2. Step 2: Convert to fraction form
    1,215.96/1,678.20 = 920.70/x
  3. Step 3: Cross multiply
    1,215.96x = 1,678.20 × 920.70
  4. Step 4: Simplify right side
    1,215.96x = 1,545,118.74
  5. Step 5: Solve for x
    x = 1,545,118.74/1,215.96
  6. Step 6: Final answer
    x = 1,270.70

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1.5x scale

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.