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Finding the Fourth Proportional to 685.28, 945.92 and 390.76

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Solution

The fourth proportional to 685.28, 945.92 and 390.76 is: 539.38

Step by Step Solution

  1. Step 1: Write the proportion equation
    685.28 : 945.92 = 390.76 : x
  2. Step 2: Convert to fraction form
    685.28/945.92 = 390.76/x
  3. Step 3: Cross multiply
    685.28x = 945.92 × 390.76
  4. Step 4: Simplify right side
    685.28x = 369,626.31
  5. Step 5: Solve for x
    x = 369,626.31/685.28
  6. Step 6: Final answer
    x = 539.38

Related Problems

Find fourth proportional to 342.64, 472.96 and 195.38
Half scale
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Double scale
Find fourth proportional to 686.28, 947.30 and 391.76
Similar ratio
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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.