This (along with geometry and algebra) can be argued to be the basis of all mathematics. Learn to add, subtract, times and divide. Also learn about factors, percentages, ratios, fractions and so on.
I will be adding a lot of material here about adding, subtracting, multiplying, dividing, fractions, ratios, factors and other basic skills. If there is something you are looking for that I have not made yet please let me know and I can push it to the top of my job-list.
One of the fundamental skills in mathematics is division, multiplication, addition and subtraction of numbers.
Does it Cancel to Zero or One (YouTube)
Bidmas Bodmas Pemdas
These stand for "Brackets Indices Division Multiplication and Subtraction", "Brackets of Division Multiplication, Addition and Subtraction" and "Parentheses, Exponents, Multiplication, Division, Addition and Subtraction".
Brackets Indices Minus Signs Challenge (Bidmas/Order of Operations) (YouTube)
Factors and Multiples
Factors are smaller and multiples are bigger!
Prime Factor Method for Lowest Common Multiple and Highest Common Factor (Explained with a Table) (YouTube)
Significant Figures/Decimal Places
Do you need 500g, 502, 502.145g or 502.144871236671123g of flour for the recipe? They are all the same number to a different number of significant figures. Probably in this case 500g is accurate enough.
How much did something increase or decrease? We can represent this using a percentage. A percentage is useful because it represents the relative change compared to the original value.
Percentage Questions Split into 4 Main Types (UP3) (YouTube)
Square roots can look really messy if written as a decimal. So they are often left as "surds".
Here is a link back to the UPmaths homepage.