Home / 42.39-63.55-21

Finding the Fourth Proportional to 42.39, 63.55 and 21

Calculator

Solution

The fourth proportional to 42.39, 63.55 and 21 is: 31.48

Step by Step Solution

  1. Step 1: Write the proportion equation
    42.39 : 63.55 = 21 : x
  2. Step 2: Convert to fraction form
    42.39/63.55 = 21/x
  3. Step 3: Cross multiply
    42.39x = 63.55 × 21
  4. Step 4: Simplify right side
    42.39x = 1,334.55
  5. Step 5: Solve for x
    x = 1,334.55/42.39
  6. Step 6: Final answer
    x = 31.48

Related Problems

Find fourth proportional to 21.20, 31.78 and 10.50
Half scale
Find fourth proportional to 84.78, 127.10 and 42
Double scale
Find fourth proportional to 43.39, 65.05 and 22
Similar ratio
Find fourth proportional to 63.59, 95.33 and 31.50
1.5x scale

Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.