Math · Arithmetic
Percentage Calculator
Calculate the percentage of a number, percentage change, increases and discounts with step-by-step solutions.
Open toolSolve percentages, rule of three, equations, functions, Pythagoras, sequences and statistics with free calculators, worked examples and straight-to-the-point theory.
Math with step-by-step solutions
Math Tools for Middle School, High School and Exams
Solve percentages, rule of three, equations, functions, Pythagoras, sequences and statistics with free calculators, worked examples and straight-to-the-point theory.
Math · Proportionality
Rule of Three Calculator
Solve direct and inverse simple rule of three. Ideal for proportions, recipes, maps and scales.
Open toolMath · Algebra
Quadratic Formula Calculator
Calculate the discriminant (Δ), the roots x₁ and x₂ and the vertex of the parabola with complete steps.
Open toolMath · Functions
Linear Function
Explore f(x) = ax + b: compute values, find the zero and visualize the behavior of the line.
Open toolMath · Functions
Quadratic Function
Analyze f(x) = ax² + bx + c: vertex, roots, concavity and table of values of the parabola.
Open toolMath · Geometry
Pythagorean Theorem
Calculate the hypotenuse or a leg of right triangles with geometric visualization and verification.
Open toolMath · Algebra
Linear Equation
Solve ax + b = c or ax + b = cx + d with step-by-step solutions. Ideal for middle school.
Open toolMath · Algebra
Linear Systems 2×2
Solve systems of two equations with two unknowns by elimination with complete steps.
Open toolMath · Sequences
Arithmetic and Geometric Sequences
Calculate the general term, sum and ratio of arithmetic and geometric progressions with a table of terms and steps.
Open toolMath · Statistics
Statistics Calculator
Calculate mean, median, mode, range, variance and standard deviation of any data set.
Open tool10 of 10 tools
Articles and study paths
Use these routes as study guides. They connect theory, examples and related tools.
How to solve a linear equation
Learn to isolate x, handle variables on both sides and check the solution.
Rule of three exercises
Practice directly and inversely proportional quantities with practical examples.
Arithmetic and geometric sequences in exams
See the general term, the sum and the patterns of sequences in entrance exam questions.
The quadratic formula and quadratic functions
Understand the discriminant, the roots, the vertex and the link between equation and parabola.
Solved exercises
Exercise 1
A T-shirt that costs $80 got a 25% discount. What is the final price?
25% of 80 = 20. Final price = 80 − 20 = $60.
Practice with the toolExercise 2
Solve 3x + 2 = x + 10.
3x − x = 10 − 2, so 2x = 8 and x = 4.
Practice with the toolExercise 3
In a right triangle with legs 6 and 8, what is the hypotenuse?
c² = 6² + 8² = 36 + 64 = 100. So c = 10.
Practice with the toolCommon mistakes in Math
- Confusing a percentage with a percentage point in successive increases and discounts.
- Using the rule of three on relationships that are not proportional.
- Applying the quadratic formula with the wrong sign in b² − 4ac.
- Calling every average a “median”; in statistics, each measure answers a different question.
Recommended pairings
To study better, follow these pairs of tools: