Question

In an isosceles triangle the base is 11 less than 3 times the length of the leg if the perimeter is 39 centimeters then find the length of the base

A. 14
B.10
C.19
D.20

Answer 1

suppose the legs are x meters each, the base is 3x-11
the perimenter: x+x+(3x-11)=39
5x=50
x=10
so the base is 3*10-11=19
the answer is C.

Answer 2

Option C
`19\ cm`

Explanation:

we know that

An isosceles triangle has two equal sides and two equal angles

Let

x------> the length of one equal side

y-----> the length of the base

The perimeter is equal to

`P=2x+y`

we have

`P=39\ cm`

so

`39=2x+y` -------> equation A

`y=3x-11` ------> equation B

substitute equation B in equation A

`39=2x+(3x-11)`

solve for y

`50=5x`

`x=10\ cm`

Find the value of y

`y=3(10)-11=19\ cm`