Arun is instructed to clap every time the count of the instructor reaches a multiple of 3. Varun is instructed to clap every time the count reaches a multiple of 7. They would clap at the same time when the count reaches
Multiples of 21
For Arun and Varun to clap together, the count has to be a multiple of both 3 and 7.
Taking the LCM of 3 and 7 which is 21. So, they will clap together every time the count reaches a multiple of 21.