Question

In a group of 20 pupils, 3 play the flute only.

Answer 1

Answer:

$\dfrac{1}{4}$

Step-by-step explanation:

Given information:

• Total number of pupils = 20
• 3 pupils play the flute
• 6 pupils play the piano only
• 6 play both instruments

We can assume that 3 pupils play the flute only as we have also been told that 6 pupils play both instruments.

To calculate the probability that a randomly chosen pupil plays neither instrument, first determine how many pupils do not play an instrument by subtracting the number of pupils who do play an instrument from the total number of pupils:

⇒ total number of pupils - pupils who play instruments

⇒ 20 - (3 + 6 + 6)

⇒ 20 - 15

⇒ 5

Therefore, 5 pupils do not play the piano and/or flute.

To calculate probability:

$\sf Probability\:of\:an\:event\:occurring = \dfrac{Number\:of\:ways\:it\:can\:occur}{Total\:number\:of\:possible\:outcomes}$

Therefore:

$\implies \textsf{Probability of a pupil playing neither instrument} = \dfrac{5}{20}=\dfrac{1}{4}$

Answer 2

Answer
5/20
0.25

Step 1
Add all pupils that play the listed instruments

6+6+3= 15

Step 2
Subtract 15 from total number of pupils

20-15= 5

Step 3
You now have a 5/20 chance of choosing a pupil that does not play a listed instrument.