Question

If A={x:x€N and x→15} B= {x;x€N and x → 3} write A and B in Roster form.​

Answer 1

Answer:

x=3n

where n is a natural number and n<8

So, n can be any digit from 1,2,3,4,5,6,7

So, in roster form

A={3,6,9,12,15,18,21}

Cardinal number = no. of distinct elements in the Set=7