On top of learning table up to eleven, but actually you only need the table of 2,3,5,7 and 11 the rest is useless as you'll simply derive it from the other one, one thing that usually helps is to multiply.

One thing that i noticed is that people have usually less trouble to estimate fraction bigger than 1 than smaller than one. For instance they would have less trouble to estimate 12/7 than 6/7.

So my advice would be to multiply to obtain something more convenient.

Another advice is to split your division.

23/36? Ok that's 20/36 +3/36. The first sum is half of 40/36 so half of 36/36+4/36. So 1+0.1+0.01+.... So 1.1 to call it short. The second part is 1/12 so 8.5%.

So practice that gymnastic both for mental calculation and on paper. During an interview, if you do this quickly on paper while at the same time explaining your process, your interviewer will actually prefer it much more than having a hard time to follow you because you do a lot of fast calculation in your head.

On top of learning table up to eleven, but actually you only need the table of 2,3,5,7 and 11 the rest is useless as you'll simply derive it from the other one, one thing that usually helps is to multiply.

One thing that i noticed is that people have usually less trouble to estimate fraction bigger than 1 than smaller than one. For instance they would have less trouble to estimate 12/7 than 6/7.

So my advice would be to multiply to obtain something more convenient.

Another advice is to split your division.

23/36? Ok that's 20/36 +3/36. The first sum is half of 40/36 so half of 36/36+4/36. So 1+0.1+0.01+.... So 1.1 to call it short. The second part is 1/12 so 8.5%.

So practice that gymnastic both for mental calculation and on paper. During an interview, if you do this quickly on paper while at the same time explaining your process, your interviewer will actually prefer it much more than having a hard time to follow you because you do a lot of fast calculation in your head.