David has a bag that holds 18 pens. 5 of the pens are ball point, 4 are gel pens and 9 are felt tip marker pens. He reaches into
2 answers:
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‣ A coin is tossed three times.
‣ The probability of getting,
1) Exactly 3 tails
2) At most 2 heads
3) At least 2 tails
4) Exactly 2 heads
5) Exactly 3 heads
★ When three coins are tossed,
then the sample space = {HHH, HHT, THH, TTH, HTH, HTT, THT, TTT}
[here H denotes head and T denotes tail]
⇒Total number of outcomes = 8
<u>1) Exactly 3 tails </u>
Here
• Favourable outcomes = {HHH} = 1
• Total outcomes = 8
<u>2) At most 2 heads</u>
[It means there can be two or one or no heads]
Here
• Favourable outcomes = {HHT, THH, HTH, TTH, HTT, THT, TTT} = 7
• Total outcomes = 8
<u>3) At least 2 tails </u>
[It means there can be two or more tails]
Here
• Favourable outcomes = {TTH, TTT, HTT, THT} = 4
• Total outcomes = 8
<u>4) Exactly 2 heads </u>
Here
• Favourable outcomes = {HTH, THH, HHT } = 3
• Total outcomes = 8
<u>5) Exactly 3 heads</u>
Here
• Favourable outcomes = {HHH} = 1
• Total outcomes = 8