Use the triangle area formula:

\(\text{Area}=\dfrac{\text{base}\times\text{height}}{2}\)

\(\text{Area}=\dfrac{5\times3}{2}=\dfrac{15}{2}=7.5\)

So the area is \(7.5\text{ cm}^2\).

A common mistake is to do \(5\times3=15\) and forget to divide by \(2\).

Use the triangle area formula:

\(\text{Area}=\dfrac{\text{base}\times\text{height}}{2}\)

\(\text{Area}=\dfrac{5\times2}{2}=\dfrac{10}{2}=5\)

So the area is \(5\text{ cm}^2\).

A common mistake is to do \(5\times2=10\) and forget to divide by \(2\).

Use the triangle area formula:

\(\text{Area}=\dfrac{\text{base}\times\text{height}}{2}\)

\(\text{Area}=\dfrac{5\times4}{2}=\dfrac{20}{2}=10\)

So the area is \(10\text{ cm}^2\).

A common mistake is to do \(5\times4=20\) and forget to divide by \(2\).

Use the triangle area formula:

\(\text{Area}=\dfrac{\text{base}\times\text{height}}{2}\)

\(\text{Area}=\dfrac{7\times3}{2}=\dfrac{21}{2}=10.5\)

So the area is \(10.5\text{ cm}^2\).

A common mistake is to do \(7\times3=21\) and forget to divide by \(2\).

Use the triangle area formula:

\(\text{Area}=\dfrac{\text{base}\times\text{height}}{2}\)

\(\text{Area}=\dfrac{6\times5}{2}=\dfrac{30}{2}=15\)

So the area is \(15\text{ cm}^2\).

A common mistake is to do \(6\times5=30\) and forget to divide by \(2\).

Use the triangle area formula:

\(\text{Area}=\dfrac{\text{base}\times\text{height}}{2}\)

\(\text{Area}=\dfrac{8\times3}{2}=\dfrac{24}{2}=12\)

So the area is \(12\text{ cm}^2\).

A common mistake is to do \(8\times3=24\) and forget to divide by \(2\).

Use the triangle area formula:

\(\text{Area}=\dfrac{\text{base}\times\text{height}}{2}\)

\(\text{Area}=\dfrac{9\times4}{2}=\dfrac{36}{2}=18\)

So the area is \(18\text{ cm}^2\).

A common mistake is to do \(9\times4=36\) and forget to divide by \(2\).

Use the triangle area formula:

\(\text{Area}=\dfrac{\text{base}\times\text{height}}{2}\)

\(\text{Area}=\dfrac{10\times7}{2}=\dfrac{70}{2}=35\)

So the area is \(35\text{ cm}^2\).

A common mistake is to do \(10\times7=70\) and forget to divide by \(2\).

Use the triangle area formula:

\(\text{Area}=\dfrac{\text{base}\times\text{height}}{2}\)

\(\text{Area}=\dfrac{12\times5}{2}=\dfrac{60}{2}=30\)

So the area is \(30\text{ cm}^2\).

A common mistake is to do \(12\times5=60\) and forget to divide by \(2\).

Use the triangle area formula:

\(\text{Area}=\dfrac{\text{base}\times\text{height}}{2}\)

\(\text{Area}=\dfrac{11\times6}{2}=\dfrac{66}{2}=33\)

So the area is \(33\text{ cm}^2\).

A common mistake is to do \(11\times6=66\) and forget to divide by \(2\).

Use the triangle area formula:

\(\text{Area}=\dfrac{\text{base}\times\text{height}}{2}\)

\(\text{Area}=\dfrac{4\times7}{2}=\dfrac{28}{2}=14\)

So the area is \(14\text{ cm}^2\).

A common mistake is to do \(4\times7=28\) and forget to divide by \(2\).

Use the triangle area formula:

\(\text{Area}=\dfrac{\text{base}\times\text{height}}{2}\)

\(\text{Area}=\dfrac{13\times2}{2}=\dfrac{26}{2}=13\)

So the area is \(13\text{ cm}^2\).

A common mistake is to do \(13\times2=26\) and forget to divide by \(2\).

Use the triangle area formula:

\(\text{Area}=\dfrac{\text{base}\times\text{height}}{2}\)

\(\text{Area}=\dfrac{15\times8}{2}=\dfrac{120}{2}=60\)

So the area is \(60\text{ cm}^2\).

A common mistake is to do \(15\times8=120\) and forget to divide by \(2\).

Use the triangle area formula:

\(\text{Area}=\dfrac{\text{base}\times\text{height}}{2}\)

\(\text{Area}=\dfrac{9\times7}{2}=\dfrac{63}{2}=31.5\)

So the area is \(31.5\text{ cm}^2\).

A common mistake is to do \(9\times7=63\) and forget to divide by \(2\).

Split the shape into a rectangle and a triangle.

The rectangle has width \(10\text{ cm}\) and height \(8\text{ cm}\).

Rectangle area \(=10\times 8=80\text{ cm}^2\).

The triangle has height \(8\text{ cm}\).

Its base is the extra length along the bottom:

\(15-10=5\text{ cm}\).

Triangle area \(=\dfrac{5\times 8}{2}=20\text{ cm}^2\).

Total area \(=80+20=100\text{ cm}^2\).

A common mistake is to forget to divide the triangle part by 2, giving \(80+40=120\text{ cm}^2\).

Split the shape into a rectangle and a triangle.

The rectangle has width \(4\text{ cm}\) and height \(8\text{ cm}\).

Rectangle area \(=4\times 8=32\text{ cm}^2\).

The triangle has base \(8\text{ cm}\) and perpendicular height \(5\text{ cm}\).

Triangle area \(=\dfrac{8\times 5}{2}=20\text{ cm}^2\).

Total area \(=32+20=52\text{ cm}^2\).

A common mistake is to forget to divide the triangle by 2, giving \(32+40=72\text{ cm}^2\).