Why in some countries the figure "7" is written with a dash or line crossing it out?

Answer 1

The line is to distinguish it from the numeral "1". Most Europeans draw a "1" not with just a vertical line, but with a tiny stroke from the top and down to the left. If you're writing quickly, it's easy to mix it up with a "7".

For similar reasons, I've seen people cross their "z"s to keep them from looking like the numeral "2".

Answer 2

When the numbers were "invented", they were signs that identified values by the number of angles within the sign.

One was a vertical bar with a diagonal bar (often shorter) sticking out towards the left. The one angle is between the two dashes.

2 was like a Z: two angles (only acute angles are counted; one does not count the "outside" obtuse angles).

3 was like a W turned with the open ends tot he left. Three angles: one inside each V and one where the two V's met.

4 ws a vertical bar with a triangle on the left: the base of the triangle did not cut across the vertical bar (i.e., not like modern fonts). 1 angle at the top, 1 at the left end of the triangle and 2 where the base of the triangle met the vertical bar.

5 was made with straight dashes: horizontal at the top, from the left end, a vertical one half-way down, a horizontal one, a vertical one downward from the right end of the middle, then a third horizontal one at the bottom (so far we have 4 angles); add a tiny vertical bar at the right side of the bottom bar, but it must not touch the middle line.

6; like 5 except that the bottom-left vertical bar does touch the middle one, adding a sixth angle.

7 was a vertical bar with 3 horizontal dashes: one at the top going off to one side only (making one angle), one in the middle going through the vertical bar (4 angles), and one at the bottom like a modern serif (2 angles). Total of seven angles.

8 was two squares, one on top of the other (each square has 4 angles).

9 was a bit complicated. It was not an upside down six.
Take an 8, bend the left side of the bottom square in half, so that the top side of that side now points inside the lower square, then add another tiny line pointing down from the end of that side. You get some kind of a hook (or a square spiral).

0 came later and fits pretty well, considering that there is no angle (i.e., zero angles) inside a circle.

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Many Europeans (and non-anglophones in North America) have retained the top left hook in the 1, the middle dash in the 7 and the tiny hook at the bottom of the 9.

Answer 3

Because they make their ones with a seraph pointing left on top. The line makes it clear to be a 7 and not a 1.

Answer 4

Because if it's written quickly it can be confused with a 1.
I do that to my 7's.

Answer 5

some people noticed that 1s and 7s look alike .to differenciate the two, some people draw a horizantal line in the center of the 7.

Answer 6

maybe they think its the proper way to write it...it's not just countries; different people have differnet ways of writing it - i switch between the 2 ways...but mathematically, i THINK it is considered the right way to write it,or something like that.

Answer 7

because thats vicks jersey number and you gotta hate him