Mathematics, 14.04.2020 14:55 hernandezbrandon059

There are 10 boys and 20 girls in Mrs Brook's class.
Mrs Brook gave all the class a test.
The mean mark for all the class is 60
The mean mark for the girls is 56
Work out the mean mark for the boys.

Answers: 2

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Answer from: Jaymp2706jj

Step-by-step explanation:

First let us consider how we calculate the mean test mark in the first place, we add up the individual test marks of the entire class to give the total test mark then we divide by the number of students. This means we need two pieces of information to calculate the boys' mean mark, the total boys' mark and the number of boys. We already know the number of boys but how do we work out the total boys' test mark? If we can work out the total class mark and total girls' mark we can find the total boys' mark by subtracting the total girls' mark from the total class mark. To do this we can work backwards to find the total mark for the whole class by taking the mean mark and multiplying it by the number of students, this gives us Total Class Mark = Mean Class Mark x Number of Students = 60 x 30 = 1800. We can do the same for the girls' mark giving us Total Girls' Mark = Mean Girls' Mark x Number of Girls = 54 x 20 = 1080. This then gives us the total boys mark as Total Boys' Mark = Total Class Mark - Total Girls' Mark = 1800 - 1080 = 720. Now we have everything we need to work out the boys' mean mark and we get Boys' Mean Mark = Total Boys' Mark/Number of Boys = 720/10 = 72.

Answer from: Quest

a) one student is chosen from classroom a, then a student is chosen from classroom b.

step-by-step explanation:

independent events are ones in which the probability of one event does not affect the probability of the second event.

one student is chosen from classroom a; this does not affect the chances of choosing a student from classroom b. this makes these independent events.

when one card is chosen from a standard deck and then set aside before a second card is chosen, the probability of the second card being chosen changes. this makes them dependent events.

when one student is chosen from classroom a and then a second student is chosen from classroom a, the probability of choosing the second student changes. this makes them dependent events.

when a letter is chosen from the alphabet and then a second letter is chosen, the probability of choosing the second letter changes. this makes them dependent events.

Answer from: Quest

mark other person brainliest

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