explain your thinking

Question

juanita has three straws that are 5 in. long and three straws that are 10 in. long. Name one combination of three straw lengths she can use to form a triangle and one combination that cannot form a triangle.

Answer 1

The two 10-inch straws can be used to form an isoceles triangle with a 5-inch straw forming the third side of the triangle.

The three 5-inch straws can be used to form an equilateral triangle. The three 10-inch straws can be used to form a larger equilateral triangle.

However, if you take two 5-inch straws and try to connect them with a 10-inch straw it won't work, since the two 5-inch straws would have to be opened to 180°.