For $5 \leq 4k +1 \leq 29$, then find the maximum number of co-primes formed from the possible values of $k$.
This is a question from the Pearson IIT foundation series for grade 8 which I am unable to solve.
I tried solving it by trying to find numbers relatively prime to each other within the given parameters. But I am struggling with the fact that when I find numbers relatively prime to each other such as $6$ and $7$, how do I continue the list of relatively prime numbers. If I add $8$ and $9$ to the mix and I take off $6$, I can add two more at the expense of one number and have them relatively prime.But this is too tedious and I hope you have some trick I can apply. But I also don't understand how this is supposed to work in the context of K.