Question

a box contains 20 discs which are numbered from 11 to 30 (11 12 13...) if 1 disc is drawn at random from the box find the probability that it bears
1) a number divisible by 7
2) a number divisible by 5 or greater than 15​

Answer 1

Answer:

here is your answer mate see the attachment

mark is as brainliest...

Answer 2

1) Probability of drawing a disc with a number divisible by 7 = 3 / 20

2) Probability of drawing a disc with a number divisible by 5 or greater than 15​ = 4 / 5

• Given,

Number of discs contained in the box = 20

Range of numbers marked on the discs = 11 to 30

• Probability of an event = Number of favourable outcomes / Total number of possible outcomes

1) A number is divisible by 7 if it is a multiple of 7.

• Therefore, numbers divisible by 7 from 11 to 30 are :

14 (7 × 2 = 14)

21 (7 × 3 = 21)

28 (7 × 4 = 28)

• Probability of drawing a disc with a number divisible by 7 on it (P₁) = Number of numbers that are divisible by 7 / Total number of discs in the box

=> P₁ = 3 / 20

2) A number is divisible by 5 if it has 0 or 5 in its units place.

• Therefore, numbers that are divisible by 5 from 11 to 30 are : 15, 20, 25, and 30

• Number of numbers divisible by 5 = 4

• Numbers greater than 15 from 11 to 30 (excluding the ones that are divisible by 5) = 16, 17, 18, 19, 21, 22, 23, 24, 26, 27, 28, and 29

• Therefore, number of numbers that are greater than 15 from 11 to 30, excluding the ones divisible by 5 = 12

• Probability of drawing a disc with a number divisible by 5 or greater than 15 (P₂) = (Number of numbers divisible by 5 + Number of numbers greater than 15) / Total number of discs

=> P₂ = (4 + 12) / 20

=> P₂ = 16 / 20

=> P₂ = 4 / 5