Home / 70.86-97.80-39.78

Finding the Fourth Proportional to 70.86, 97.80 and 39.78

Calculator

Solution

The fourth proportional to 70.86, 97.80 and 39.78 is: 54.89

Step by Step Solution

  1. Step 1: Write the proportion equation
    70.86 : 97.80 = 39.78 : x
  2. Step 2: Convert to fraction form
    70.86/97.80 = 39.78/x
  3. Step 3: Cross multiply
    70.86x = 97.80 × 39.78
  4. Step 4: Simplify right side
    70.86x = 3,889.80
  5. Step 5: Solve for x
    x = 3,889.80/70.86
  6. Step 6: Final answer
    x = 54.89

Related Problems

Find fourth proportional to 35.43, 48.90 and 19.89
Half scale
Find fourth proportional to 141.72, 195.59 and 79.55
Double scale
Find fourth proportional to 71.86, 99.18 and 40.78
Similar ratio
Find fourth proportional to 106.29, 146.69 and 59.66
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.