Y9 - Christmas Test Review Homwork

Percentages of amounts:

To find 10% divide by 10

To find 1% divide by 100

To find 50% divide by 2

To find 25% divide by 4

 

Use these to help you calculate any percentage by building percentages

Example:

Find 32% of 80

 

10% of 80 = 80  ÷ 10 = 8

1% of 80 = 80  ÷  100 = 0.8

 

32% = 10% + 10% + 10% + 1% + 1%

        =  8     +  8    + 8     + 0.8  + 0.8

       = 25.6
 

 

Rounding:

When rounding remember the rhyme

5 and above give it a shove, 4 and below down we go …

Examples:

Round to 1 decimal place

a) 4.57

The number next to the first decimal place (the 7) is above 5 so we round the number in the first decimal place up to 7.

Answer: 4.6

 

Round to 2 decimal places

b) 0.83192

The number next to the second decimal place (the 1) is below 5 so we don’t change the number in the second decimal place,

Answer: 0.83

 

Significant Figures

A significant figure is any digit that is not a zero at the beginning or end of a number.

The number 560 has 2 significant figures the number 506 has 3 significant figures.

 

When rounding to a number of significant figures use the same rules as above but first decide what it is you are rounding to.

 

For example rounding 5673 to 1 significant figure, the 5 is in the first significant figure and is in the thousands column so we round to the nearest thousand the answer is 6000

 

0.3178  rounded to 1 significant figure is 0.3 as the first significant figure is 1 decimal place.

Multiplying and dividing by numbers between 0 and 1

Remember multiplying by 0.1 is the same as dividing by 10
dividing by 0.1 is the same as multiplying by 10.

Example:
68 x 0.1 = 68 ÷ 10 = 6.8

 

68 ÷ 0.1 = 68 x 10 = 680

 

ANGLES

 

Angles at a point = 360^o

Adjacent angles on a line = 180^o

Angles in a triangle = 180^o

Angles in a quadrilateral = 360^o

In Parallel lines

Corresponding angles are the ones on the shelf that you can slide up and down and are equal

Alternate angles are in the corners on opposite sides and are equal

 

DATA:

Averages & Range

Mean: Add up all the numbers and divide by how many are in the list

Median: The middle of an ordered list

Mode: The most popular number

Range: Highest subtract lowest

 

Pie Charts:

Find the total frequency

360 ÷ (Total frequency) = ?

Take each frequency and multiply by ? to work out the angle to draw.

 

If your angels don't add to 360 degrees you've done something wrong