Classify the triangle with angles 40∘, 60∘ and 80∘
Look at the largest angle: 80.
It is under 90, so every angle is.
The answer is Acute.
Where students go wrong
Calling a triangle acute because two of its angles are. It only takes one angle of 90 or more to make it right or obtuse, so the largest angle is the only one worth checking.
Also called triangle classification, types of triangles or acute obtuse right.
Questions about these worksheets
Yes. Every classifying triangles sheet is free to print and free to download as a PDF. There is no account to make, no email to hand over and no limit on how many you take.
Yes. The answer key prints on a second page, and you can choose whether it shows each question beside its answer or just the answers in a list.
Yes. Print straight from the page, or download the PDF and print that. The sheet is laid out for paper rather than squeezed off a screen, so there is room to work under each question, and the answer key comes out on its own page.
Pre-Algebra is usually taken around 7th or 8th grade, though schools vary and plenty of students meet it earlier or later. Pick the difficulty rather than the grade: the easy level suits a first lesson on it, the hard level suits review before a test.
Yes, as many as you like. The questions are built fresh each time rather than picked from a fixed set of files, so pressing Generate gives a new sheet. That is what you want for a second class, a retake, or two students sitting next to each other.
That is the closest comparison, and Kuta Software is good software. It is also paid software you install on a computer. These worksheets run in a browser tab for free, with no account and nothing to install. Like Kuta, the classifying triangles questions are generated when you ask for them rather than pulled from a fixed set of files, so two classes never get the same sheet, and the answer key comes with it.
Yes. There are three levels, and you can tick more than one for a sheet that mixes them, in which case the questions come out easiest first. The harder levels are not just larger numbers: they ask for something the easy ones do not.
Calling a triangle acute because two of its angles are. It only takes one angle of 90 or more to make it right or obtuse, so the largest angle is the only one worth checking.