Question 50

Jambmaths question: 

If U ={x: x is an integer and 1≤ x ≤ 20}

E1 = {x: x is a multiple of 3}

E2 = {x: x is a multiple of 4}

and an integer is picked at random from U,  find the probability that it is not in E2

 

Option A: 

$\tfrac{3}{4}$

Option B: 

$\tfrac{3}{10}$

Option C: 

$\tfrac{1}{4}$

Option D: 

$\tfrac{1}{20}$

Jamb Maths Solution: 

$\begin{align}  & U=\{1,2,3,---20\} \\ & n(U)=20,\text{  } \\ & {{E}_{1}}=\{3,6,9,12,15,18\},\text{ }n({{E}_{1}})=6 \\ & {{E}_{2}}=\{4,8,12,16,20\},\text{   }n({{E}_{2}})=5 \\ & E_{2}^{1}=\{1,2,3,5,6,7,9,10,11,13,14,15,17,18,19\} \\ & P({{E}_{2}})=\frac{15}{20}=\frac{3}{4} \\\end{align}$

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