Learn Math
Nadia Rahmawati
Math Curriculum Team, Algonova
A plane shape is a two-dimensional figure with only length and width, no thickness, so it can be drawn completely on paper.
The difference from a solid shape is simple: plane shapes have area, solids have volume. A square can be drawn; a cube can only be drawn as if.
| Shape | Key property | Perimeter | Area |
|---|---|---|---|
| Square | 4 equal sides, 4 right angles | 4 × side | side × side |
| Rectangle | Opposite sides equal, 4 right angles | 2 × (l + w) | l × w |
| Triangle | 3 sides, angles total 180 degrees | sum of 3 sides | ½ × base × height |
| Parallelogram | Opposite sides parallel and equal | 2 × (a + b) | base × height |
| Trapezium | One pair of parallel sides | sum of 4 sides | ½ × (a + b) × height |
| Rhombus | 4 equal sides, perpendicular diagonals | 4 × side | ½ × d1 × d2 |
| Kite | Two pairs of adjacent equal sides | 2 × (a + b) | ½ × d1 × d2 |
| Circle | All points equidistant from the centre | 2 × π × r | π × r × r |
Perimeter is the length of the fence around a garden. Area is how much grass is inside it.
One is measured in units of length such as centimetres, the other in square units such as square centimetres. If the final answer carries square units, what was computed is area.
This anchor resolves most of the confusion, because the commonest error is not the wrong formula but choosing the wrong one for what the question asked.
Eight area formulas look like a lot, but three of them are one family:
A child who sees this pattern needs to remember three things rather than eight.
So the formulas in the table do not stay as rote memory, here are three examples worked step by step.
Example 1: rectangle. A garden is 12 m long and 8 m wide.
Example 2: right triangle. Base 8 cm, height 6 cm, hypotenuse 10 cm.
Example 3: circle. A wheel has a diameter of 14 cm, use π = 22/7. The radius is 14 ÷ 2 = 7 cm.
The pattern is always the same: write the formula, insert the known numbers, then calculate. The most common slip happens when inserting numbers, for example forgetting to convert the diameter to a radius before calculating a circle. To build understanding, ask the child to draw the shape on grid paper first and link it to real objects, such as the perimeter of a desk or the floor area of a room.
Yes, Algonova Indonesia offers a complete math program for kids aged 6 to 17, covering all school levels from primary, junior high, to senior high. Each level has a dedicated curriculum aligned with the child's cognitive stage and the Indonesian school curriculum (Kurikulum Merdeka). For primary school (6-12): basic operations, fractions, simple geometry, and introduction to algebra. For junior and senior high (13-17): algebra, quadratic equations, basic trigonometry, advanced geometry, basic calculus, statistics, UTBK SNBT preparation, and advanced topics. All classes are online live with certified teachers in small groups of up to 10 students per class. Our method is built on visual conceptual understanding, not formula memorisation. Try a free trial class for a child's level diagnostic and recommended learning path.
Yes. For mathematics Algonova Indonesia offers a free diagnostic session of about 60 minutes with no commitment. The format is called Metode Diagnostik Algonova. No credit card is needed and there is no auto subscription afterwards. Note that these roughly 60 minutes are a diagnostic session, not a regular class. A regular math class runs 90 minutes, while the coding and design tracks have their own introductory format, a free 60 minute master class. During the diagnostic a certified teacher maps the child's level: which topics are already solid and where the gaps sit. The child also tries the online learning platform and works through first problems matched to their school level. After the session parents receive a personal learning plan based on the diagnostic result, plus a transparent explanation of program, schedule, and pricing from Rp 102,000 per lesson. To book, fill in the form on the website.
Algonova Indonesia math classes come in three formats: 1-on-1 private, a mini-group of 2–4 kids, and a group of up to 10 students with similar ability and school grade levels. This small group format is deliberately chosen because it provides the optimal balance between social interaction with peers and personal teacher attention. In a mini-group, every child averages about 10 minutes of direct teacher interaction in a single session. Compare with traditional offline bimbel typically of 20-40 students per class — direct interaction there is only 1-2 minutes per child, or none at all. For families wanting full attention, one-on-one private class format is also available with one student per teacher. This format is more intensive and suits competition preparation, catching up from severe gaps, or specific topic depth.
Kids math tutoring at Algonova Indonesia starts from Rp 102,000 per lesson. The price includes a live session with a certified teacher, digital learning materials, online platform access, and an official certificate upon completing each program level. The transparent 'starting from' rate is the same across all school levels — the final quote depends only on class format (private, mini-group, or group) and how many sessions per week you choose. Groups are the most affordable option; private classes are more intensive and suit competition prep or closing larger gaps. Full pricing details are shared transparently after the free trial class. No surprise fees — every cost component is explained before formal enrolment. To receive the latest pricing details, fill in the booking form on the website.
Yes, all Algonova Indonesia math programs are fully available online with live sessions taught by certified teachers — not recorded videos. Kids learn in real time in small groups of up to 10 students, with two-way interaction, live Q&A, and problems worked on alongside the teacher throughout the class. To join online class, a child only needs a computer or laptop with a camera, a stable internet connection, and a headset. The Algonova platform runs directly in the browser so no special software installation is required. Kids can write problems in a regular notebook or on a tablet with stylus. Because every class is fully online, families can join from anywhere in Indonesia and easily fit lessons around school and other activities.
Three main factors make Algonova math tutoring effective for Indonesian kids. First, the curriculum aligns with Kurikulum Merdeka used in national schools, so what is learned at Algonova directly helps with school lessons and exams. Second, the methodology is built on visual conceptual understanding (not formula memorisation). Kids learn to break big problems into small systematic steps — a thinking pattern transferable to other subjects like science and IT. Third, small groups of up to 10 students per class let teachers adjust pace to each child's ability. Slower kids get personal help, while faster kids don't get bored waiting. The result: most Algonova students see math grade improvements at school within the first 2-3 months.
Algonova Indonesia is specifically designed to help kids behind catch up in a way that doesn't make them feel defeated or ashamed. Every new student starts with a free diagnostic during the trial class to identify exactly where the gap occurred. Based on the diagnostic, the teacher builds a personal learning path that closes the gap from the most basic foundation. For example, a junior high student weak in algebra might actually be behind in primary school fraction operations. We go back to the foundation, then progress gradually without comparison with other peers. Many Algonova students who initially started 1-2 grade levels behind successfully caught up and even surpassed classmates within 3-6 months with weekly classes and consistent homework. It's never too late to start. Try a free trial class for diagnosis without commitment.
A plane shape is a two-dimensional figure with only length and width and no thickness, so it can be drawn completely on paper. Plane shapes have area; solid shapes have volume.
Eight are taught at school: the square, rectangle, triangle, parallelogram, trapezium, rhombus, kite, and circle.
Perimeter is the length of the fence around a garden; area is how much grass is inside. Perimeter is measured in units of length such as centimetres, area in square units such as square centimetres. If the answer carries square units, it is area.
There is a pattern that cuts the memorising. Rectangle, parallelogram, and square are all base times height. A triangle is half a rectangle, because two identical triangles form one. Rhombus and kite are both half the product of the diagonals.
Because textbooks draw the height as a dashed line inside the shape while the sloping side is far more visible. Height is always perpendicular to the base. The habit that saves you: label the base and height before entering any numbers.
Shape recognition starts in Years 1 and 2. Perimeter and area by counting squares in Year 3, then the formulas in Year 4. Trapeziums, rhombuses, kites, and circles in Years 5 and 6. Shape properties and proofs in Year 7.
Every plane shape has two symmetry properties that come up in tests:
The easiest check is with real paper: cut the shape out, then fold and turn it. A minute with scissors teaches more than a diagram in a book.
Mistake number two happens because textbooks draw the height as a dashed line inside the shape while the sloping side is far more visible. The habit that saves you: label the base and the height before putting any numbers into a formula.
| Year | What is covered |
|---|---|
| 1–2 | Recognising and sorting shapes |
| 3 | Perimeter and area by counting unit squares |
| 4 | Perimeter and area formulas for squares, rectangles, triangles |
| 5–6 | Trapeziums, parallelograms, rhombuses, kites, circles |
| 7 | Shape properties and their proofs, angle relationships |
Full topic lists are in Year 4 primary maths and Year 7 secondary maths. For three-dimensional figures, see solid shapes.
The area of a trapezium is A = ½ × (a + b) × h, where a and b are the two parallel sides and h is the height, the perpendicular distance between them. A trapezium with parallel sides of 8 cm and 12 cm and a height of 6 cm:
The most common mistake is adding all four sides when only the two parallel sides are used, or using the slanted side as the height.
| Shape | Lines of symmetry | Rotational symmetry |
|---|---|---|
| Square | 4 | 4 |
| Rectangle | 2 | 2 |
| Equilateral triangle | 3 | 3 |
| Isosceles triangle | 1 | 1 |
| Scalene triangle | 0 | 1 |
| Parallelogram | 0 | 2 |
| Rhombus | 2 | 2 |
| Kite | 1 | 1 |
| Isosceles trapezium | 1 | 1 |
| Circle | infinite | infinite |
For regular shapes, lines of symmetry equal the order of rotational symmetry, which equals the number of sides. Every plane shape has rotational symmetry of at least 1, because after a full 360° turn it returns to its starting position. The two rows most often wrong: a parallelogram has 0 lines of symmetry but rotational symmetry of 2, and a scalene triangle has 0 lines of symmetry but still rotational symmetry of 1.
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