GRADE 8 MENTAL MATH - 3

Instructions:

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

Speak the question out loud, calculate the answer in your head, then write your answer.

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

QUESTIONS

1) Simplify this expression:

2) Find a simplified algebraic expression for the perimeter of an equilateral triangle in which each side measures 2x + 1 cm.

3) What is the sum of the exterior angles of a decagon?

4) What is the numerical value of ?

5) The rule of a transformation is: ( x, y ) g ( x, y – 2 ). Find the image coordinates of (–8, 5)?

6) The area of a circle sector is one third the area of the circle. What is the measure of the central angle of this sector?

7) The circumference of a circle is meters. What is the length of the radius?

8) Using H for Heads and T for Tails, list the 4 possible outcomes if we toss 2 coins only once.

9) If 80% of the tickets sold in a lottery say "Sorry, try again" -- what is the probability of winning a prize?

10) Which numbered triangle is the image of the shaded triangle after a refection in the y-axis? (write triangle 1, 2 or 3 for your answer)

Solutions

1) 9x + 3 2) 6x + 3 3) 360° 4) 8 5) ( – 8, 3 )
6) 120° 7) r = 5 m 8) HH, HT, TH, TT 9) 20% or 1 in 5 10) triangle 3

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