Carcass wrote:
Which of the following could be the perimeter of an isosceles triangle if one side has length 3 inches and another side has length 7 inches?
Indicate all possible perimeters.
A. 9 inches
B. 11 inches
C. 13 inches
D. 15 inches
E. 17 inches
F. 19 inches
Source: 320 GRE Math Questions
Positive difference of other 2 sides < Third sides < Sum of other 2 sides
Case I:
3 - 3 < 7 < 3 + 3
0 < 7 < 6
Not valid - So perimeter cannot be 13
Case II:
7-7 < 3 < 7 + 7
0 < 3 < 14
A valid case - So perimeter can be 17
Hence, option E only