GRADE 8 MENTAL MATH - 1

Instructions:

Grab pencil and paper. In a column, list the numbers 1 to 10.

Calculators are not allowed. All calculations must be done in your head and not on paper!

QUESTIONS

1) Calculate 20% of 50.

2) If 6 cans of juice cost \$3, how much will 18 cans cost?

3) Which of these ratios is the GREATEST?
A) 3 : 2 .......... B) 3 : 4 .......... C) 4 : 2 .......... D) 2 : 3

4) The circumference of a circle is 400 cm. How long is the arc subtended by a 90° central angle?

5) Rectangle A is 3 cm wide and 4 cm long. Rectangle B is 1 cm wide and 6 cm long.
What is the ratio of the area of rectangle A to the area of rectangle B? (reduce to lowest terms).

6) These triangles are similar. What is the length of the missing side?

7) What is the ratio of similarity for the transformation shown here?

8) The circular lid of a soup can has an area of cm². What is its radius?

9) Collect like terms to simplify ......... 6a + 4 + 7a – 9 – 2a

10) We apply the transformation r(O, 180°) to the shaded triangle. Which triangle is the image of this transformation? (write triangle 1, 2 or 3 for your answer)

Solutions

 1) 10 2) \$9 3) C) 4 : 2 4) 100 cm. 5) 12 : 6 = 2 : 1 6) 24 7) OA:OA' = 4:1 8) r = 5 cm 9) 11a – 5 10) triangle 2