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Finding the Fourth Proportional to 1,390.68, 1,920.24 and 860.34

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Solution

The fourth proportional to 1,390.68, 1,920.24 and 860.34 is: 1,187.95

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,390.68 : 1,920.24 = 860.34 : x
  2. Step 2: Convert to fraction form
    1,390.68/1,920.24 = 860.34/x
  3. Step 3: Cross multiply
    1,390.68x = 1,920.24 × 860.34
  4. Step 4: Simplify right side
    1,390.68x = 1,652,059.28
  5. Step 5: Solve for x
    x = 1,652,059.28/1,390.68
  6. Step 6: Final answer
    x = 1,187.95

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Half scale
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Double scale
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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.