Correcting Common Mistakes
The formula for area of a circle is π×radius².
Bob does the following work:
Radius = 3 in
Area = π × 3²
= 3.14×6
= 18.84 in²
The formula for area of a triangle is
½×base×height
1) What mistake did Bob make? Explain in a
complete sentence.
Bob does the following work:
Base = 8 m
Height = 6 m
Area = ½ × 8 × 6
=4x6
= 24 m²
1) What mistake did Bob make? Explain in a
complete sentence.
2) Solve the problem correctly.
2) Solve the problem correctly.
The formula for circumference of a circle is
2×π×radius or π×diameter
The formula for volume of a pyramid is
⅓×Area of base×height
Bob does the following work:
Radius = 8 cm
Circumference = 2×π×8
= 16×3.14
= 50.24 cm
1) What mistake did Bob make? Explain in a
complete sentence.
2) Solve the problem correctly.
Bob does the following work:
Area of base = 10 x 8 = 80 in²
Volume = 80 x 6 = 480 in³
1) What mistake did Bob make? Explain in a
complete sentence.
2) Solve the problem correctly.
The formula for area of a circle is π×radius².
To find the surface area of a 3D object, find the area
of each side and add them all together.
Bob does the following work:
Radius = 10 cm
Area = π × 10²
= 3.14×100
= 314 cm²
Bob does the following work:
Surface Area = 7 × 5 × 2
= 35 × 2
= 70 cm²
1) What mistake did Bob make? Explain in a
complete sentence.
1) What mistake did Bob make? Explain in a
complete sentence.
2) Solve the problem correctly.
2) Solve the problem correctly.
To find the perimeter of a shape, add up the lengths
of the sides.
The formula for volume of a prism is
Area of base×height
Bob does the following work:
Perimeter = 10 + 6 + 8 + 5
= 29 m²
1) What mistake did Bob make? Explain in a
complete sentence.
Bob does the following work:
Area of base = 3 x 4 = 12 yd²
Volume = 12 x 5 = 60 yd³
1) What mistake did Bob make? Explain in a
complete sentence.
2) Solve the problem correctly.
2) Solve the problem correctly.