math
posted by billy on .
find n(A)for each set
A={1/2, 1/2, 1/3, 1/3,..., 1/10, 1/10}

what is n(a set)?

looks like the fractions from 1/2 , 1/3 . ... 1/10 come in pairs with their negatives,
I count 18 of them 
n(A) is the cardinal of the sets and how did you get the #18

o ok i got it 1/2 1/3 1/4 1/5 1/6 1/7 1/8 1/9 1/10 thanks