A triangle has a side lengths of 18cm, 80 cm and 81cm. Classify it as acute obtuse or right?

It is acute.

Step-by-step explanation:

81^2 = 6561

80^2 = 6400

18^2 = 324

80^2 + 18^2 = 6724

So 81^2 < 80^2 + 18^2, therefore the triangle is acute.

NOTE: In a triangle with sides a, b and c with a = longest side,

if a^2 b^2 + c^2.

Step-by-step explanation: 1st you are going to have to see ... if it less than 90 it it is acute, if its directly at 90 it would be right ... or, if the # is greater rhan 90 its obtuse, so if it is 18,80, and 81 what would it be remember ... DO NOT ADD