Basil asks 40 students how many books they bought last year. the chart shows information about the number of books they each bought. a) what is the percentage of those students who bought 20 or more books?

b) work out an estimate for the mean number of books bought.
please show the full working out.
Number of students who bought 0-4 books= 9
number of students who bought 5-9 books= 10
number of studenst who bought 10-14 books= 13
number of students who bought 15-19 books= 2
number of studenst who bought 20-24 books= 6
please show the full working out

Step-by-step explanation:

Probability is the likelihood or chance that an event will occur.

Probability = number of expected outcome/total outcome.

a)Total number of student is the total outcome = 40

Expected number of outcome is the number of students who bought 20 or more books = 6 (number of students who bought 20-24 books)

Probability of those students who bought 20 or more books =  6/40 = 0.15

Expressing as percentage = 0.15 * 100 = 15%

This means that 15% of the total students bought 20 or more books

b) Mean is calculated using the formula

f is the frequency

x is the midpoint of the class interval

N is the total number of students.

Check the attachment for the frequency table.

Mean number of books bought is 10.25

5x + 3y = - 4

step-by-step explanation:

the equation of a line in standard form is

ax + by = c ( a is a positive integer and b, c are integers )

express the line first of all in slope- intercept form

y = mx + c ( m is the slope and c the y-intercept )

to calculate m use the gradient formula

m = ( y₂ - y₁ ) / ( x₂ - x₁ )

with (x₁, y₁ ) = (7, - 3) and (x₂, y₂ ) = (4, - 8)

m = = -

y = - x + c ← is the partial equation

to find c substitute either of the 2 points into the partial equation

using (4, - 8 ), then

- 8 = - + c ⇒ c = -

y = - x - ← in slope-intercept form

multiply all terms by 3 to eliminate the fractions

3y = - 5x - 4 ( add 5x to both sides )

5x + 3y = - 4 ← in standard form