Home / 4-21

Finding the Third Proportional to 4 and 21

Calculator

Solution

The third proportional to 4 and 21 is: 110.25

Step by Step Solution

  1. Step 1: Write the proportion equation
    4 : 21 = 21 : x
  2. Step 2: Convert to fraction form
    4/21 = 21/x
  3. Step 3: Cross multiply
    4x = 21 × 21
  4. Step 4: Simplify right side
    4x = 441
  5. Step 5: Solve for x
    x = 441/4
  6. Step 6: Final answer
    x = 110.25

Related Problems

Find third proportional to 2 and 10.50
Half scale
Find third proportional to 8 and 42
Double scale
Find third proportional to 6 and 32
Similar ratio
Find third proportional to 6 and 31.50
1.5x scale

Why These Related Problems?

These problems maintain the same ratio (5.25) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.