Question

5 cm

3 cm
Which face has an area of 28 cm2?
5 cm
3 cm
Face
4 cm
7 cm
А
B
с
7 cm
E

Answer 1

Face B has an area of 28 cm2

Explanation:

Area of a Rectangle

Given a rectangle with dimensions X and Y, the area of the rectangle is calculated as:

A=X*Y

Area of a Triangle

Given a triangle with dimensions X and Y, the area of the triangle is calculated as:

`\displaystyle A=(X*Y)/(2)`

We need to find the face of the figure with an area of 28 cm2. A quick look can give us the solution since we only need to find a shape of dimensions 7 and 4. Face B is the only one to have an area of 28 cm2. Let's try them all:

Face A: Rectangle of dimensions 5 cm, 7 cm. Area=5*7=35 cm2. Incorrect

Face B: Rectangle of dimensions 4 cm, 7 cm. Area=4*7=28 cm2. Correct

Face C: Rectangle of dimensions 3 cm, 7 cm. Area=3*7=21 cm2. Incorrect

Face D: Triangle of dimensions 3 cm, 4 cm. Area=3*4/2=6 cm2. Incorrect

Face E: Apparently a triangle congruent to face D. If so, Incorrect

Face B has an area of 28 cm2