Can two numbers have $15$ as their HCF and $220$ as their LCM?

In a school, students are to be divided into groups of $10,$ $15$ and $18$. Find the least number of students required to form such groups.

Three frogs take $150$ $\mathrm{cm}$, $125$ $\mathrm{cm}$ and $84$ $\mathrm{cm}$ long jumps. If they jump together from a point, at what distance will they jump together again?

Ramesh wants to make flags from three ribbons of lengths, $240$ $\mathrm{cm}$, $318$ $\mathrm{cm}$ and $426$ $\mathrm{cm}$. He has to cut the strings into pieces of equal lengths. What is the greatest possible length of each piece?

Write two numbers whose LCM is $4$ and sum is $5$.

Find the lowest common multiple of $18$ and $24$.