Question

The perimeter of an isosceles triangle is $40$ units. If the length of one of the equal sides is $12$ units, then determine the length of the third side.

• A. $24$ units
• B. $16$ units
• C. $21$ units
• D. $12$ units

Answer 1

The correct option is B $16$ units


An isosceles triangle has two equal sides.
Length of one equal side $=12$ units

Given:
AC = $12$ units
$\therefore$ AB = $12$ units

Sum of the two equal sides, i.e., AB and AC $=12+12=24$ units

Length of side $3=$ Perimeter – Sum of two equal sides
$=(40-24)$ units
$=16$ units

Therefore, the length of the third unequal side $=16$ units