if s= {a,b,c,d} where a={ }, b={a,b}, c={a,c} and d={a,b,c}. show that u is a binary operation on s but n is not
In how many ways 5 boys and 5 girls may be arranged around a table so that no two girls sit together?
The angle of elevation of an aeroplane from a point on the ground is 60° .After a flight of 30 sec the angle of elevation becomes 30°. If the aeroplane is flying at a constant height of 3000√3 m, find the speed of the aeroplane.