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Finding the Fourth Proportional to 989.40, 1,364.64 and 639.72

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Solution

The fourth proportional to 989.40, 1,364.64 and 639.72 is: 882.34

Step by Step Solution

  1. Step 1: Write the proportion equation
    989.40 : 1,364.64 = 639.72 : x
  2. Step 2: Convert to fraction form
    989.40/1,364.64 = 639.72/x
  3. Step 3: Cross multiply
    989.40x = 1,364.64 × 639.72
  4. Step 4: Simplify right side
    989.40x = 872,987.50
  5. Step 5: Solve for x
    x = 872,987.50/989.40
  6. Step 6: Final answer
    x = 882.34

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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.