무료 강의 50개, 유아부터 삼각법까지
당신의 방식으로 수학 배우기
어린이·청소년·성인을 위한 무료 쉬운 수학 강의 — 이제 세기부터 삼각법까지 전 과정을 다룹니다. 모든 강의에 채점되는 연습 문제와 대화형 다이어그램이 있습니다.
학년별 보기
저학년 (K–2)
- 덧셈과 뺄셈
- 자릿값
- 세기에서 곱셈으로
- 구구단과 나눗셈
- 분수와 소수
- 둘레와 넓이
- 약수와 소수
- 음수와 연산 순서
- 변수와 방정식
- 비와 백분율
- 각·삼각형·원
- 통계 기초
- 그래프·연립·이차방정식
- 다항식과 인수분해
- 피타고라스와 삼각법
- 확률과 경우의 수
- 양방향 암산
- 어림과 문장제
- 이진수·부동소수점·나머지
산수 — 양방향으로
Addition — carry right
The classic column method: ones first, carry to the left.
Addition — biggest first
Left-to-right addition: hundreds, then tens, then ones.
Subtraction — borrow right
The standard borrowing method, step by step.
Subtraction — left to right
Count down by chunks, or biggest column first.
Multiplication — standard way
Right-to-left multiplying with carrying.
Multiplication — biggest first
Partial products left to right — the mental-math way.
Division
Long division, short division, and chunking.
대수
Variables & expressions
Letters that hold numbers — evaluate and translate.
One-step equations
Undo one thing: the balance rule that starts algebra.
Two-step equations
Undo in reverse order — with step-by-step checking.
Inequalities
<, >, ≤, ≥ — and the one rule that flips the sign.
Exponents & powers
Repeated multiplication, the three rules, x⁰ and x⁻ⁿ.
Square roots
Perfect squares, estimating, and simplifying √12.
Polynomials
Terms, degrees, like terms, and distributing.
Factoring
GCF, x²+bx+c, and difference of squares.
Graphing lines
y = mx + b — slope and intercept on the plane.
Systems of equations
Substitution, elimination, and where lines meet.
Quadratic equations
Parabolas, zero-product, and the formula that always works.
기하
Angles & lines
Acute to straight, complements, parallel lines.
Triangles
The 180° rule, families, and why bridges trust them.
Quadrilaterals
The four-sided family tree and the 360° rule.
Circles
Radius, diameter, π — C = πd and A = πr².
Perimeter & area
Around vs inside — with unit-square grids.
Surface area & volume
Wrapping vs filling — boxes, cylinders, unit³.
The coordinate plane
(x, y) addresses, quadrants, distance.
Transformations
Slide, flip, spin, scale on the grid.
Pythagorean theorem
a² + b² = c², triples, and the distance formula.
Similarity & congruence
Same shape, different size — scale factors.
수와 구조
Place value & bases
Why 467 means 400 + 60 + 7 — and how binary works.
Fractions
What numerator & denominator mean, adding, comparing.
Decimals & percents
Place value past the point; everyday percent tricks.
Negative numbers
The number line, and why neg×neg = pos.
Order of operations
PEMDAS honestly — including the ambiguous case.
Factors & primes
Divisibility tricks and prime factorization.
비·자료·확률
Ratios & proportions
Comparing quantities and cross-multiplying.
Unit rates & percents
Per hour, per dollar — and the better-deal test.
Statistics basics
Mean, median, mode, range — and when the mean lies.
Spread & deviation
Variance and standard deviation as 'typical distance.'
Probability basics
0 to 1 — favorable/total, complements, AND/OR rules.
Counting principles
Permutations, combinations, factorials.
삼각법
sin, cos, tan
SOH-CAH-TOA on right triangles — sides and angles.
The unit circle
(cos, sin) as a point — and the free identity.
사고력
Estimation & rounding
Front-end estimating and Fermi problems.
Word problems
Pólya's four-step method for attacking any problem.
Data, averages & graphs
Mean vs median — and how charts can politely lie.
과학과 컴퓨팅의 수학
Scientific notation & SI
Writing the universe's biggest and smallest numbers.
Measurement & error
Accuracy vs precision, significant figures, honest numbers.
Math inside computers
Binary, bits, floating point — and 0.1 + 0.2 ≠ 0.3.
Binary & hexadecimal
How computers count — $FF and 0x10 explained.
Floating point
Why 0.1 + 0.2 ≠ 0.3 — and the integer-cents trick.
Modular arithmetic
Clock math — MOD, parity tests, wrap-around indexing.
두 방향, 같은 답
대부분의 교과서는 오른쪽에서 왼쪽으로만 가르칩니다. 하지만 숙련된 암산가들은 종종 반대로 큰 자리부터 계산합니다. 어느 쪽이 낫다기보다, 같은 산수를 다른 끝에서 보는 것입니다.
왜 두 가지 방법인가?
연구에 따르면 아이들이 스스로 만든 왼쪽→오른쪽 전략은 흔하며 자릿값 이해를 높입니다. →