SChand Composite Mathematics Class 7 Chapter 16 Chance and Probability Exercise 16B

  Exercise 16 B

Question 1 

Refer to the shape chart and fill in the blanks in the following table giving the probability of touching each figure. One is done for you.

(Diagram to be added)

$\begin{array}{|c|c|c|c|c|c|}\hline \text { (i) } & \text { (ii) } & \text { (iii) } & \text { (iv) } & \text { (v) } & \text { (vi) } \\\hline \frac{15}{32} & \frac{8}{32} \text { ar } \frac{1}{4} & \frac{4}{32} \text { or } \frac{1}{8}& \frac{3}{32} & \frac{1}{32} & \frac{1}{32} \\\hline\end{array}$

Question 2

A box contains 4 packs of chocolates. Shruti takes out a pack without looking at the packs. What is the chance (probability) that she picks:

(a) Perk

(b) Kitkat

2 Kitkat

1 Perk

1 Dairy milk

 

Sol: Probability=  $\frac{Number of successful outcomes }{Number of possible outcomes}$

$\frac{1}{4}$

Question 3

A jar has one blue and 9 green marbles in it. What is the probability of drawing

(a) a green marble ?

(b) a blue marble?

(diagram to be added)

Sol: (a) $p=\frac{9}{10}$

(b) $p=\frac{1}{10}$

Question 4

The six faces of a cube are numbered from 1 to 6 . The cube is rolled. What is the chance that it will land with :

(a) a 4 up

(b) a 2 up? 

Sol: (a)  $p=\frac{1}{6}$

(b) $p=\frac{1}{6}$

Question 5

Five girls put their names in a box. They are anjali , Haze, Ayushree, Ishita and Rashi. Rashi draws a name from the box. What is the chance that she draws her own name? 

Ans: $p=\frac{1}{5}$

Question 6

An ordinary pack of $5 z$ cards is well shuffled. The top card is then turned over. What is the probability that :

(a) the top card will be a red card.

(b) the top card is a number card.

[Clue : How many red cards are there? How many number cards are there ?]

Sol: (a) Number of Outcomes = 26 

$P=\frac{26}{52}$ or $\frac{1}{2}$

(b) Total Number card $=9 \times 4=36$

$P=\frac{36}{52}$ or $\frac{9}{13}$

Question 7

A gift pack of chips contains 2 cheese and onion, 2 plain salted, 3 Masala munch and 1 Pudina. Tanya takes out a pack of chips without looking at the packs. What is the chance that she picks :

(a) plain salted

(b) Masala

(c) Cheese and onion

(d) Pudina

Sol: (a) $p=\frac{2}{8}$ or $\frac{1}{4}$

(b) $p=\frac{3}{8}$

(c) $P=\frac{2}{8}$ or $\frac{1}{4}$

(d) $p=\frac{1}{8}$

Question 8

An ordinary die is rolled. What is the probability that the number of dots on its upper face is

(a) 3

(b) less than 3

(c) an even number

(d) 7 ?

Sol: (a) $p=\frac{1}{6}$

(b) $\frac{2}{6}$ or $\frac{1}{3}$

(c) $\frac{3}{6}$ or $\frac{1}{2}$

(d) $\frac{0}{6}$

Question 9

A jar contains 3 white, 4 blue, 5 red and 2 green marbles. If a marble is drawn at random from the jar, what is the probability that the marble is :

(a) white

(b) red

(c) blue

(e) not white

(f) not red?

(d) green

 

Sol;  (a) $p=\frac{3}{14}$

(b) $p=\frac{5}{14}$

(c) $p=\frac{4}{14}$ or $\frac{2}{7}$

(d) $p=\frac{2}{14}$ or $\frac{1}{7}$

(e) $p=\frac{14-3}{14}=\frac{11}{14}$

Question 10

Draw a probability scale. Mark each of these outcomes on your scale.

Give reasons for your answers.

(a) The school bus will break down tomorrow.

(b) The next baby to be born will be a boy.

(c) An ice cube will melt when it is left outside on a hot day.

(d) A heavy stone will float when it is dropped in the sea.

(e) The winner of the women's Olympic 100 meter final will be aged under 35 years.

(Diagram to be added)

Question 11

- Ashita has 20 movies in her video collection and 5 of the movies feature her favourite actor. If she randomly choses a movie, what is the probability that she will choose one featuring her favourite actor ?

(a) $\frac{1}{5}$

(b) $\frac{1}{4}$

(c) $\frac{3}{4}$

(d) $\frac{3}{5}$

Question 12

A card is drawn from a pack of 100 cards numbered 1 to 100 . Find the probability of drawing a square number. 

(a) $\frac{1}{10}$

(b) $\frac{9}{10}$

(c) $\frac{1}{5}$

(d) $\frac{2}{5}$

Question 13

During a class survey, it was found out that cheese pizza is the favourite snack for 30 out 40 students. Which per cent is closest to the probability that a student's favourite snack is cheese pizza ?

(a) $50 \%$

(b) $60 \%$

(c) $75 \%$

(d) $80 \%$

Question 14

High order thinking skills ( Hots )

You roll a die. Write the probability of rolling a prime number as a decimal.