Sum or difference of two spinners/dice

Questions where the random variable is defined as the sum or difference of the outcomes from two spinners or dice.

4 questions

CAIE S1 2015 November Q6
6 A fair spinner \(A\) has edges numbered \(1,2,3,3\). A fair spinner \(B\) has edges numbered \(- 3 , - 2 , - 1,1\). Each spinner is spun. The number on the edge that the spinner comes to rest on is noted. Let \(X\) be the sum of the numbers for the two spinners.
  1. Copy and complete the table showing the possible values of \(X\).
    Spinner \(A\)
    \cline { 2 - 6 }1233
    Spinner \(B\)- 2
    - 21
    - 1
    1
  2. Draw up a table showing the probability distribution of \(X\).
  3. Find \(\operatorname { Var } ( X )\).
  4. Find the probability that \(X\) is even, given that \(X\) is positive.
CAIE S1 2018 November Q6
6 A fair red spinner has 4 sides, numbered 1,2,3,4. A fair blue spinner has 3 sides, numbered 1,2,3. When a spinner is spun, the score is the number on the side on which it lands. The spinners are spun at the same time. The random variable \(X\) denotes the score on the red spinner minus the score on the blue spinner.
  1. Draw up the probability distribution table for \(X\).
  2. Find \(\operatorname { Var } ( X )\).
  3. Find the probability that \(X\) is equal to 1 , given that \(X\) is non-zero.
CAIE S1 2018 November Q2
2 A fair 6 -sided die has the numbers \(- 1 , - 1,0,0,1,2\) on its faces. A fair 3 -sided spinner has edges numbered \(- 1,0,1\). The die is thrown and the spinner is spun. The number on the uppermost face of the die and the number on the edge on which the spinner comes to rest are noted. The sum of these two numbers is denoted by \(X\).
  1. Draw up a table showing the probability distribution of \(X\).
  2. Find \(\operatorname { Var } ( X )\).
CAIE S1 2019 November Q5
5 A fair red spinner has four sides, numbered 1, 2, 3, 3. A fair blue spinner has three sides, numbered \(- 1,0,2\). When a spinner is spun, the score is the number on the side on which it lands. The spinners are spun at the same time. The random variable \(X\) denotes the score on the red spinner minus the score on the blue spinner.
  1. Draw up the probability distribution table for \(X\).
  2. Find \(\operatorname { Var } ( X )\).