Jen brought some sesame bagels and some plain bagels .the ratio of the number of sesame bagels to the number of plain bagels is 1: 3 what fraction of bagles are plain? ,what percent of the bagels are plain, if jill bought 2dozen bagels, how many of each type of bagel did she buy? pls give the explanation how did you get the answer of these three

Let S be the number of sesame bagels and P be the number of plain bagels.

The ratio of 1:3 means that if we divide S by P, whatever values they assume, we get 1:3; which means that there are always 3 plain bagels for each sesame bagel.

In the simplest case we will have 4 bagels, from which 3 are plain and one is sesame, therefore, we will have 3 out of 4 bagels which are plain, that is: 3/4 of the bagels are plain. 

3/4 is equivalent to having 3 parts of a WHOLE or UNIT, which was divided by 4. If we divide 1 by 4 we get 0.25 and if we get 3 of those 0.25 parts we have 0.75. That means our WHOLE or UNIT of bagels is composed of 0.75 plain bagels. To know how much bagels are plain in a pack of 100 bagels, just multiply the ratio 0.75 by the amount of the WHOLE of a 100:

100*0.75 = 75 percent, that is 75 of 100 bagels are plain.

If Jill bought 2 dozen bagels we just have to multiply by the ratio again to find the amount of plain ones:

(2*12)*0.75 = 18 plain bagels

Notice that if we wanted to find the amount of sesame bagels, we would just have to use 0.25 instead of 0.75, since those are the only 2 types of bagels forming the whole of 1.