A fraction consists of two parts, a numerator and a denominator. When typesetting permits, they are written with the numerator over the denominator and the division bar between, for example:

1

2

When you "invert" a fraction, to express its reciprocal, for example, you replace the numerator with the denominator and vice versa. You effectively turn it upside down, the same as when you invert a bottle or jar or anything else.

2

1

When typesetting does not permit a fraction to be written vertically, we use the "slash" character (/) to express the division.

The inverse of 1/2 is 2/1.

1

2

When you "invert" a fraction, to express its reciprocal, for example, you replace the numerator with the denominator and vice versa. You effectively turn it upside down, the same as when you invert a bottle or jar or anything else.

2

1

When typesetting does not permit a fraction to be written vertically, we use the "slash" character (/) to express the division.

The inverse of 1/2 is 2/1.