Given,
A={1,3,4,6,9}&B={2,4,5,8,10}
And relation is given by,
R=(a1,b1),(a2,b2):a1≤b2 andb1≤a2
Now taking cases for a1≤b2 we get,
a1=1,b2∈2,4,5,8,10→5cases
a1=3,b2∈4,5,8,10→4cases
a1=4,b2∈4,5,8,10→4cases
a1=6,b2∈8,10→2cases
a1=9,b2∈10→1cases
So, total 16 cases will be there
Now finding cases of b1≤a2 we get,
b1=2,a2∈3,4,6,9→4cases
b1=4,a2∈4,6,9→3cases
b1=5,a2∈6,9→2cases
b1=8,a2∈9→1cases
So, here total 10 cases,
Hence, total elements in relation =16×10=160