If x = {n2+1:n is a positive integer and 1 ≤ n ≤ 5},
Y = {5n:n is a positive integer and 1 ≤ n ≤ 5}, find x ∩ y.
A.
{5,10}
B.
{5, 10, 15}
C.
{2, 5, 10}
D.
{5, 10, 15, 20}
Correct Answer: {5,10}
Explanation
X = {n2 +1:n is a positive integer and 1 ≤ n ≤ 5}
Implies X = {2, 5, 10, 17, 26} i.e. put n= 1, 2, 3, 4 and 5
Y = {5n:n is a positive integer and 1 ≤ n ≤ 5}
Put X = 1, 2, 3, 4, and 5
Y = {5, 10, 15, 20, 25}
X ∩ Y = {2, 5, 10, 17, 26} ∩ {5, 10, 15, 20, 25}
= {5, 10}
X = {n2 +1:n is a positive integer and 1 ≤ n ≤ 5}
Implies X = {2, 5, 10, 17, 26} i.e. put n= 1, 2, 3, 4 and 5
Y = {5n:n is a positive integer and 1 ≤ n ≤ 5}
Put X = 1, 2, 3, 4, and 5
Y = {5, 10, 15, 20, 25}
X ∩ Y = {2, 5, 10, 17, 26} ∩ {5, 10, 15, 20, 25}
= {5, 10}
