Probability from two-way tables

The Maths Habit

45 students: 20 are boys.
12 boys and 15 girls walk to school.
How many girls do not walk?
10
60 people chose tea or coffee. 34 chose tea. 26 were adults, and 18 adults chose coffee. How many children chose tea?
26
A café sold 80 drinks. 50 were hot. 22 hot and 9 cold drinks were sold in the morning. How many were sold in the afternoon?
49

One student is picked at random.
Is it more likely to be a girl or someone who takes the bus?

	Walk	Bus	Total
Boys	8	6	14
Girls	9	7	16
Total	17	13	30

A girl: 16 girls, but only 13 take the bus

Find P(Year 8 who chose juice).

	Tea	Juice	Total
Year 7	8	14	22
Year 8	11	17	28
Total	19	31	50

P =1750the ones you want

everyoneAnswer1750

Find P(child who swam).

	Swim	Gym	Total
Adults	9	7	16
Children	15	5	20
Total	24	12	36

P =1536the ones you want

everyoneAnswer512

Find P(Year 8 who chose juice).

	Tea	Juice	Total
Year 7	8	14	22
Year 8	11	17	28
Total	19	31	50

P =1750the ones you want

everyoneAnswer1750

Find P(late).

	Late	On time	Total
Monday	2	22	24
Tuesday	7	17	24
Total	9	39	48

P =948the ones you want

everyoneAnswer316

Find P(Year 8 who chose juice).

	Tea	Juice	Total
Year 7	8	14	22
Year 8	11	17	28
Total	19	31	50

P =1750the ones you want

everyoneAnswer1750

Find P(girl who chose art).

	Art	Music	Total
Boys	9	13	22
Girls	12	6	18
Total	21	19	40

P =1240the ones you want

everyoneAnswer310

Find P(Year 8 who chose juice).

	Tea	Juice	Total
Year 7	8	14	22
Year 8	11	17	28
Total	19	31	50

P =1750the ones you want

everyoneAnswer1750

Find P(hockey).

	Hockey	Netball	Total
Year 9	21	9	30
Year 10	13	17	30
Total	34	26	60

P =3460the ones you want

everyoneAnswer1730

Find P(Year 8 who chose juice).

	Tea	Juice	Total
Year 7	8	14	22
Year 8	11	17	28
Total	19	31	50

P =1750the ones you want

everyoneAnswer1750

Find P(coach).

	Single	Return	Total
Train	18	27	45
Coach	6	21	27
Total	24	48	72

P =2772the ones you want

everyoneAnswer38

Probability from two-way tables worksheet, page 1

Answer sheet

A table shows 40 students. 15 girls walk and 10 boys walk. One is picked at random. Find P(does not walk).
38
A table shows 12 boys and 18 girls. P(boy who has a pet) = 15. How many boys have a pet?
6

One student is picked at random.
Walk Cycle Total
Year 7 13 9 22
Year 8 11 17 28
Total 24 26 50
Find P(Year 8 student who cycles).
1750
Use the table above. Find P(walks).
2450 = 1225
Rob says P(Year 7) = 2228. Is Rob right? Explain.
No: 2250, out of all 50

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