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Finding the Fourth Proportional to 1,187, 1,638.24 and 721.16

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Solution

The fourth proportional to 1,187, 1,638.24 and 721.16 is: 995.31

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,187 : 1,638.24 = 721.16 : x
  2. Step 2: Convert to fraction form
    1,187/1,638.24 = 721.16/x
  3. Step 3: Cross multiply
    1,187x = 1,638.24 × 721.16
  4. Step 4: Simplify right side
    1,187x = 1,181,433.16
  5. Step 5: Solve for x
    x = 1,181,433.16/1,187
  6. Step 6: Final answer
    x = 995.31

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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.