Home / 891.78-1,231.02-643.20

Finding the Fourth Proportional to 891.78, 1,231.02 and 643.20

Calculator

Solution

The fourth proportional to 891.78, 1,231.02 and 643.20 is: 887.88

Step by Step Solution

  1. Step 1: Write the proportion equation
    891.78 : 1,231.02 = 643.20 : x
  2. Step 2: Convert to fraction form
    891.78/1,231.02 = 643.20/x
  3. Step 3: Cross multiply
    891.78x = 1,231.02 × 643.20
  4. Step 4: Simplify right side
    891.78x = 791,792.06
  5. Step 5: Solve for x
    x = 791,792.06/891.78
  6. Step 6: Final answer
    x = 887.88

Related Problems

Find fourth proportional to 445.89, 615.51 and 321.60
Half scale
Find fourth proportional to 1,783.56, 2,462.04 and 1,286.40
Double scale
Find fourth proportional to 892.78, 1,232.40 and 644.20
Similar ratio
Find fourth proportional to 1,337.67, 1,846.53 and 964.80
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.