Arithmentic

Question 1

Even & odds

Answer 1

1. Even + even = even
2. Odd + odd = even
3. Even + odd = odd
4. Even x Even = even
5. Odd x Odd = even
6. Even x Odd = even

Question 2

Prime numbers

Answer 2

A number that only has two positive divisors: 1 and itself.
The first ten prime numbers are:

2, 3, 5, 7, 11, 17, 19, 23 & 29.

Question 3

Rules of roots

Answer 3

Question 4

Decimals

Answer 4

Question 5

Ratio (scale up)

Answer 5

If you need to find an equivalent ratio, multiply or divide both terms by the same number.

Example: 3:5 → Multiply by 2 → 6:10.

Question 6

Find total parts of ratio

Answer 6

If a ratio represents parts of a whole, sum the parts and use it to find individual values.

Example: If a total of 60 is divided in a 2:3 ratio, the sum is 2+3=5. Each part is 60 \div 5 = 12, so the values are 2 \times 12 = 24 and 3 \times 12 = 36.

Question 7

Ratio (missing values)

Answer 7

If a ratio involves an unknown, set up an equation.
Example: If x:4 = 6:8, solve for x.
Cross multiply: x \times 8 = 6 \times 4 → 8x = 24 → x = 3.

Question 8

Percent: find part of whole

Answer 8

If the part is x and the whole is y:

X (part) / y (whole)

Question 9

Percent: find % of whole

Answer 9

(% decimal) (whole) = part

Question 10

Percent: x part is what % of y number?

Answer 10

(Part) (% decimal) = whole

Question 11

Percents bigger than 100%

Answer 11

Question 12

Percent change

Answer 12

Increase:

(Increase - base) / Base = decimal *100

Decrease:

(Base - decrease) / base = decimal*100

Note: when computing increase, the base is the smaller number. When computing decrease, the base is the larger number