Question

7. Suppose we represent the distance above the ground by a positive integer and the ground by a negative integer, then answer the following:

i. An elevator descends into a mine shaft at the rate of 6 metre per minute. What will be its position after one hour?

ii. If it begins to descend from 15 m above the ground, what will be its position after 45 minutes?
8. In a class test containing 20 questions, 5 marks are given for every correct answer and (–2) marks are given for every incorrect answer.

i) Anu attempts all questions but only 8 of her answers are correct. What is her total score?

(ii) One of her friends gets only 6 answers correct. What will be her score?

9. . In a test + 3 marks are given for every correct answer and –1 mark are given for every incorrect answer. Sona attempted all the questions and scored +20 marks though she got 10 correct answer

1. How many incorrect answer has she attempted?

2. How many questions were given in the test?

Answer 1

Answer:

7

i) -360 metre

ii) -255 metre

8

i)16

ii)4

Step-by-step explanation:

7

i) speed of decending elevator = -6 mt/ min {Since the lift is decending downwards negative sign is used to signify the position}

As we know that distance = time X speed

therefore position after 1 hour i.e... 60 minutes = 60 x 6 mt/min = -360 metre

ii) position difference after 45 min = 45minutes X 6 metre/ minute = 270

Since the elevator desends  from 15 mt above the ground

therefore position = -270+15 = -255 metre under the ground

8

i) if only 8 of her answers are correct then positive marking = 5x8= 40

number of wrong questions= 20-8= 12

negative marking for the wrong answer = 12 x -2 = -24

therefore total score = 40 + (-24)

=40-24

=16

ii) if only 6 of her answers are correct then positive marking = 5x6= 30

number of wrong questions= 20-6= 14

negative marking for the wrong answer = 14 x -2 = -26

therefore total score = 30 + (-26)

=30-26

=4