A string of length 21 cm is vibrating with 3 loops. The separation between node and immediate antinode will be?

Here, in the given problem we can see that at the two ends nodes are formed, keeping 3 loops are formed in mind.

here, 3 antinodes are formed in 21 cm long string& in total 6 segments of NA(node-antinode distance)

so the distance between node and antinode=21/6=3.5 cm