Nathan cut an isosceles triangle from felt to make a spirit banner. Two sides of his banner had the following measures : 15 inches and 7 inches. Which could be the measure of the third side of Nathan’s banner ?
Accepted Solution
A:
The third side must be 15 inches.
Since the triangle is isosceles, two sides are the same length. This gives us the choices of 7 inches or 15 inches.
The triangle inequality theorem tells us that the sum of the smaller two sides must be greater than the length of the third side. If we have 7, 7 and 15, this does not work, because 7+7 is not greater than 15. Thus the missing side must be 15 inches.