Number Topics

Question 1

Estimating

Answer 1

Round to ONE significant figure

Question 2

Decimals multiplying and dividing

Answer 2

1) Ignore decimal point and multiply
2) Count digits after decimal in question
3) Put decimal point in answer

e.g

0.3 x 0.2 = 0.06
3 x 2 = 6

(two digits after decimal point in question (.3 and .2)

Question 3

Best Buy

Answer 3

Cost / amount (in pence)

Question 4

Simple Interest

Answer 4

Find interest in one year by doing amount / 100 x % and then use that answer and multiply by the years in the question

e.g

Regina invests £380 in an account which pays 3% simple interest each year. How much interest will she earn in 4 years?

One year = 380 / 100 x 3 = £11.40
Four years = 4 x £11.40 = £45.60

Question 5

Compound Interest

Answer 5

Work out the multiplier by adding the initial % to 100, but write it as a decimal. Multiply this number with the initial investment and continue to multiply your answer with the multiplier

Compound decay (depreciation) is same formula, but SUBTRACT the % from 100.

Question 6

Direct Proportion

Answer 6

Divide the price by the quantity to find the price of one, and then use this answer and multiply with the quantity you are looking for.

Round up if answer is a decimal

e.g

Emma is handing out some leaflets. She gets paid per leaflet she hands out. If she hands out 300 leaflets she will get £2.40. How many leaflets will she gave to hand out to earn £8.50?

To earn £1: 300 / £2.40 = 125
To earn £8.50: 125 x £8.50 = 1063

Question 7

Ratio - Finding out who has more money than who

Work out:

Pat and Julie share some money in the ratio 2:5. Julie gets £45 more than Pat. How much money does Pat get?

Answer 7

2:5

5-2 = 3
45/3 = 15
15x2 = 30

Question 8

Percentage Change

Answer 8

Change / Original x 100

Question 9

Percentages, Decimals and Fractions

Answer 9

• Decimal to Percentage - Multiply by 100
• Percentage to Decimal and Fraction - Divide by 100
• Fraction to Decimal - Divide the numerator with the denominator
• Decimal to Fraction - If there are two digits, multiply by 10. If there are three digits, multiply by 100. If there are four digits, Multiply by 1000

Question 10

Percentages (without a calculator)

Answer 10

50% = / 2

25% = / 4

10% = / 10

1% = / 100

Question 11

Fractions: Multiplying

Answer 11

Multiply the numerators together

Multiply the denominators together

Question 12

Fractions: Adding and Subtracting

Answer 12

If the denominators are the same, add the numerators only.

If the denominators are different, find a common denominator by multiplying both top and bottom of each fraction by the other sides denominator and then add the numerators as normal.

Question 13

Directed Numbers

Answer 13

Multiplying:

P x P = P
N x N = P
P x N = N
N x P = N

Dividing:

P / P = P
N / N = P
P / N = N
N / P = N

Adding:

P + P = P
N + N = N
N + P = N
P + N = N

Subtracting:

N - P = N
P - N = P
N - N = N
P - P = P

Question 14

First 10 Cube numbers

Answer 14

1
8
27
64
125
216
343
512
729
1000

Question 15

How do you find a prime?

Answer 15

Divide each one by 3 + 7, if it’s a decimal then it’s prime

Question 16

Prime numbers list ( up to 97 )

Answer 16

2 , 3 , 5 , 7
11 , 13 , 17 , 19
23 , 29
31 , 37
41 , 43 , 47
53 , 59
61 , 67
71 , 73 , 79
83 , 89
97

Question 17

Equation for (Probability) when all outcomes are equally likely

Answer 17

Probability = Number of ways for something to happen / Total number of possible outcomes

Question 18

Relative frequency equation:

Answer 18

FREQUENCY / NUMBER OF WAYS YOU TRIED THE EXPERIMENT

Question 19

Allied angles

Answer 19

Add up to 180°

Found in C or U shapes

Question 20

Vectors

Answer 20

If TOP is POSITIVE, move RIGHT
If TOP is NEGATIVE, move LEFT

If BOTTOM is POSITIVE, move UP
If BOTTOM is NEGATIVE, move DOWN

Question 21

Input and Output

Answer 21

Forwards = Multiply and Add

Backwards = Divide and Subtract

Question 22

Hours to minutes

Minutes in an hour into seconds

Answer 22

1 hour = 60 minutes

60 minutes = 3600 seconds