Direct Proportion Practice Problems and Solutions Online

Master direct proportionality with step-by-step practice problems. Learn to identify, calculate, and solve direct proportion relationships in real-world scenarios.

📚Master Direct Proportion with Interactive Practice
  • Identify direct proportional relationships using multiplication and division patterns
  • Calculate missing values in direct proportion tables and equations
  • Solve real-world problems involving time, distance, and cost proportions
  • Verify proportionality by checking if ratios remain constant
  • Apply the Y = aX formula to graph direct proportion relationships
  • Distinguish between direct and non-proportional relationships in word problems

Understanding Direct Proportion

Complete explanation with examples

What is direct proportion?

Direct proportionality indicates a situation in which, when one term is multiplied by a certain amount, the same exact thing happens to the second term.

In the same way, when one term is divided by a certain amount, the same exact thing happens to the second term.

The ratio between both magnitudes remains constant.

Let's observe an example that illustrates this concept.

Direct Proportion in a table

Detailed explanation

Practice Direct Proportion

Test your knowledge with 3 quizzes

How many times longer is the radius of the red circle than the radius of the blue circle?

210

Examples with solutions for Direct Proportion

Step-by-step solutions included
Exercise #1

If there are 18 balls in a box of which 23 \frac{2}{3} are white:

How many white balls are there in the box in total?

Step-by-Step Solution

To solve this problem, we will determine the number of white balls in the box using a fraction of the total number of balls.

We are given the total number of balls in the box as 18, and we know that 23 \frac{2}{3} of these balls are white. To find the number of white balls, we follow these steps:

  • Step 1: Identify the total quantity, which is 18 balls.
  • Step 2: Use the given fraction 23 \frac{2}{3} to find the number of white balls.
  • Step 3: Multiply the total number of balls by the fraction of white balls: 18×23 18 \times \frac{2}{3} .

Perform the calculation:

18×23=18×0.6667=12 18 \times \frac{2}{3} = 18 \times 0.6667 = 12

Alternatively, calculate directly using fractions:

18×23=18×23=363=12 18 \times \frac{2}{3} = \frac{18 \times 2}{3} = \frac{36}{3} = 12

Thus, the total number of white balls in the box is 12.

Therefore, the correct answer is choice 12.

Answer:

12

Video Solution
Exercise #2

In a box there are 28 balls, 14 \frac{1}{4} of which are orange.

How many orange balls are there in the box in total?

Step-by-Step Solution

To solve this problem, we'll determine the number of orange balls by calculating the fraction of the total number of balls:

  • Step 1: Identify the total number of balls, 28 28 .
  • Step 2: Note the fraction representing the orange balls, 14 \frac{1}{4} .
  • Step 3: Apply the formula to find the number of orange balls:
    Number of orange balls =28×14 = 28 \times \frac{1}{4}

Now, let's perform the calculation:
28×14=28÷4=7 28 \times \frac{1}{4} = 28 \div 4 = 7

Therefore, the number of orange balls in the box is 7 7 .

Answer:

7

Video Solution
Exercise #3

There are two circles.

One circle has a radius of 4 cm, while the other circle has a radius of 10 cm.

How many times greater is the area of the second circle than the area of the first circle?

Step-by-Step Solution

The area of a circle is calculated using the following formula:

where r represents the radius.

Using the formula, we calculate the areas of the circles:

Circle 1:

π*4² =

π16

Circle 2:

π*10² =

π100

To calculate how much larger one circle is than the other (in other words - what is the ratio between them)

All we need to do is divide one area by the other.

100/16 =

6.25

Therefore the answer is 6 and a quarter!

Answer:

614 6\frac{1}{4}

Video Solution
Exercise #4

The rectangle ABCD is shown below.

AB = X

The ratio between AB and BC is x2 \sqrt{\frac{x}{2}} .


The length of diagonal AC is labelled m.

XXXmmmAAABBBCCCDDD

Determine the value of m:

Step-by-Step Solution

We know that:

ABBC=x2 \frac{AB}{BC}=\sqrt{\frac{x}{2}}

We also know that AB equals X.

First, we will substitute the given data into the formula accordingly:

xBC=x2 \frac{x}{BC}=\frac{\sqrt{x}}{\sqrt{2}}

x2=BCx x\sqrt{2}=BC\sqrt{x}

x2x=BC \frac{x\sqrt{2}}{\sqrt{x}}=BC

x×x×2x=BC \frac{\sqrt{x}\times\sqrt{x}\times\sqrt{2}}{\sqrt{x}}=BC

x×2=BC \sqrt{x}\times\sqrt{2}=BC

Now let's look at triangle ABC and use the Pythagorean theorem:

AB2+BC2=AC2 AB^2+BC^2=AC^2

We substitute in our known values:

x2+(x×2)2=m2 x^2+(\sqrt{x}\times\sqrt{2})^2=m^2

x2+x×2=m2 x^2+x\times2=m^2

Finally, we will add 1 to both sides:

x2+2x+1=m2+1 x^2+2x+1=m^2+1

(x+1)2=m2+1 (x+1)^2=m^2+1

Answer:

m2+1=(x+1)2 m^2+1=(x+1)^2

Video Solution
Exercise #5

Given the rectangle ABCD

AB=X the ratio between AB and BC is equal tox2 \sqrt{\frac{x}{2}}

We mark the length of the diagonal A A with m m

Check the correct argument:

XXXmmmAAABBBCCCDDD

Step-by-Step Solution

Let's find side BC

Based on what we're given:

ABBC=xBC=x2 \frac{AB}{BC}=\frac{x}{BC}=\sqrt{\frac{x}{2}}

xBC=x2 \frac{x}{BC}=\frac{\sqrt{x}}{\sqrt{2}}

2x=xBC \sqrt{2}x=\sqrt{x}BC

Let's divide by square root x:

2×xx=BC \frac{\sqrt{2}\times x}{\sqrt{x}}=BC

2×x×xx=BC \frac{\sqrt{2}\times\sqrt{x}\times\sqrt{x}}{\sqrt{x}}=BC

Let's reduce the numerator and denominator by square root x:

2x=BC \sqrt{2}\sqrt{x}=BC

We'll use the Pythagorean theorem to calculate the area of triangle ABC:

AB2+BC2=AC2 AB^2+BC^2=AC^2

Let's substitute what we're given:

x2+(2x)2=m2 x^2+(\sqrt{2}\sqrt{x})^2=m^2

x2+2x=m2 x^2+2x=m^2

Answer:

x2+2x=m2 x^2+2x=m^2

Video Solution

Frequently Asked Questions

What is direct proportion and how do I identify it?

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Direct proportion occurs when two quantities increase or decrease by the same factor. To identify it, check if when one value multiplies by a number, the other value also multiplies by the same number, keeping their ratio constant.

How do I solve direct proportion word problems step by step?

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1. Create a table with the given values 2. Check if both quantities change by the same multiplication factor 3. Use the relationship Y = aX to find the constant 'a' 4. Apply this constant to calculate unknown values

What's the difference between direct proportion and regular ratios?

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In direct proportion, the ratio between quantities stays constant as values change. Regular ratios just compare two quantities at one point in time without considering how they change together.

Why isn't a monthly fee plus per-transaction charge direct proportion?

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Fixed fees break direct proportionality because when transactions double, the total cost doesn't double due to the constant monthly fee. Direct proportion requires both quantities to change by exactly the same factor.

How do I graph direct proportion relationships?

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Direct proportion graphs are straight lines passing through the origin (0,0) following Y = aX. The slope 'a' represents the constant of proportionality between the two variables.

What are common real-life examples of direct proportion?

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• Distance traveled and time (at constant speed) • Cost and quantity of identical items • Worker hours and total wages (at fixed hourly rate) • Recipe ingredients when scaling portions

How do I check if my direct proportion answer is correct?

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Verify by calculating the ratio Y/X for different pairs of values. If all ratios are equal, you have direct proportion. Also check that when one value doubles, the other also doubles.

What mistakes should I avoid in direct proportion problems?

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Don't confuse correlation with proportion. Avoid assuming direct proportion when there are fixed costs or fees involved. Always verify that both quantities change by the same multiplication factor, not just that they both increase.

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