The meaning of dot centered vertically, as in $3\cdot 5$

Question

I just went to a site to practise some maths as I am studying some maths on my OU course in computing and IT and I ran into some symbols that I did not understand

The questions were

1. solve $16+14/2+3\cdot 5-11$ (the point was placed halfway between the top and bottom of the numbers)

2. $(11-5)\cdot (63-59+6)/12$, once again point is halfway between top and bottom

Can someone explain what this means if it is different to a decimal point?

Also this symbol was used in other questions $|$ and I was wondering what this meant as well

In context it was the number $-5$ can be written as and one answer was $|-5|$ and another choice was $-|-4|-1$

Answer 1

It is common to use $a \cdot b$ to denote multiplication of $a$ and $b$; it means the same as $a \times b$.

The notation $|-4|$ means the absolute value of $-4$. It is $4$; one ignores the sign. Formally it is defined as $|a|= a$ if $a \ge 0$ and $|a|= -a$ if $a < 0$.

Answer 2

Computer Science usually work to BODMAS, i.e. "Brackets Off, Division, Multiplication, Addition, and Subtraction." Work through the operations of the formula in this order and you shouldn't go far wrong.

By the way, $a\cdot b$ is commonly written to mean $a\times b$.

Brackets indicate factors which can be multiplied out, e.g. $$(a+b)\cdot c = a\cdot c + b\cdot c.$$

See also quid's answer for further information.

Answer 3

Well, we all know that in algebra, the multiplication sign is often omitted because of the variable $x$. That sign in between your two numbers avoids confusion while multiplying, so that's a multiplication sign. So, $3\cdot x$ is also known as $3x$. Also, it's different from a decimal point because it's specifically up higher and, like I told you, it's also used to indicated multiplication. Also, $5\cdot6=30$, so see? It's up higher than a regular decimal point.