Question

account?
C.
b. An elevator ascends at the rate of 5 m/s. If it
starts from the basement which is 5 m below
the ground level, in how much time will it
reach a height of 50 m above the ground?
In a class test having 20 questions, 2 marks
are given for a correct answer and (-2) for
every incorrect answer. How many marks
will a student get if he attempts all questions
but gets only 14 correct?
2​

Answer 1

Answer:

Ncert solutions

Grade 7

Mathematics

Science

Chapters in NCERT Solutions - Mathematics, Class 7

Exercises in Integers

Question 7

Q7) An elevator descends into a mine shaft at the rate of 6 m/min. If the descent starts from 10 m above the ground level, how long will it take to reach – 350 m.

Solution

Transcript

Solution 7:

Starting position of mine shaft is = 10m above ground

but,

it moves in opposite direction so it travels the distance (-350 m ) below the ground.

Total distance covered by mine shaft = 10m - (-350m)

= 10 + 350

= 360m

Now, taken to cover a distance of 6m by it = 1 minute

Time taken to cover a distance of 1m by it = \frac{1}{6\ }\min

6

1

min

Therefore, tie taken to a cover a distance of 360m = \frac{1}{6}\times\ 360\ =\ 60\ \min\ \

6

1

× 360 = 60 min

60 minutes = 1 hour

thus, in one hour the mine shraft reaches = 350 below the ground.