Question

Someone help please! I'm a confoosed bab:(

Answer 1

Answer:

$\huge\boxed{A_{\triangle RST}=9units^2}$

Step-by-step explanation:

(Look at the picture).

Calculate the area of the rectangle and subtract the areas of red triangles.

The formula of an area of a rectangle:

$A_{\boxed{\ }}=a\cdot b$

We have:

$a=5,\ b=4$

substitute:

$A_{\boxed{\ }}=5\cdot4=20$

The formula of an area of a triangle:

$A_\triangle=\dfrac{a\cdot h}{2}$

substitute:

$A_1=\dfrac{3\cdot3}{2}=\dfrac{9}{2}=4.5\\\\A_2=\dfrac{2\cdot4}{2}=\dfrac{8}{2}=4\\\\A_3=\dfrac{5\cdot1}{2}=\dfrac{5}{2}=2.5\\\\A_1+A_2+A_3=4.5+4+2.5=11$

Area of ΔRST:

$A_{\triangle RST}=A_{\boxed{\ }}-(A_1+A_2++A_3)$

substitute:

$A_{\triangle RST}=20-11=9$