There are 42 rolls in the cafeteria.

How can they be divided into 2 groups so that they are in a ratio of 2:5. How many rolls will be in each group?

You would have atleast 21 rolls in each gruop.

42 can be divided by 7 to be 6, right?

That means you have 7 groups of 6 rolls each.

So, if you want to separate those rolls into 2 groups for a 2:5 ratio, (note: 2:5 is 7 groupings total), then you'd put 12 rolls into one group and 30 in the other group.