Home / 420.78-579.84-280.74

Finding the Fourth Proportional to 420.78, 579.84 and 280.74

Calculator

Solution

The fourth proportional to 420.78, 579.84 and 280.74 is: 386.86

Step by Step Solution

  1. Step 1: Write the proportion equation
    420.78 : 579.84 = 280.74 : x
  2. Step 2: Convert to fraction form
    420.78/579.84 = 280.74/x
  3. Step 3: Cross multiply
    420.78x = 579.84 × 280.74
  4. Step 4: Simplify right side
    420.78x = 162,784.28
  5. Step 5: Solve for x
    x = 162,784.28/420.78
  6. Step 6: Final answer
    x = 386.86

Related Problems

Find fourth proportional to 210.39, 289.92 and 140.37
Half scale
Find fourth proportional to 841.56, 1,159.68 and 561.48
Double scale
Find fourth proportional to 421.78, 581.22 and 281.74
Similar ratio
Find fourth proportional to 631.17, 869.76 and 421.11
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.