Question

10. A water tank has steps inside it. A monkey is sitting on the topmost step (i.e., the first
step). The water level is at the ninth step.
(1) He jumps 3 steps down and then jumps back 2 steps up.
In how many jumps will he reach the water level?
(i) After drinking water, he wants to go back. For this, he
jumps 4 steps up and then jumps back 2 steps down
in every move. In how many jumps will he reach back
the top step?
(i) If the number of steps moved down is represented by
negative integers and the number of steps moved up by
positive integers, represent his moves in part (i) and (ii)
by completing the following: (a) – 3 + 2 - ... - 8
(b) 4-2+ ... = 8. In (a) the sum(-8) represents going
down by eight steps. So, what will the sum 8 in (b)
represent?​

Answer 1

Step-by-step explanation:

i) The position of monkey after the

1st jump J1 is at 4th step ↓

2nd jump J2 is at 2nd step ↑

3rd jump J3 is at 5th step ↓

4th jump J4 is at 3rd step ↑

5th jump J5 is at 6th step ↓

6th jump J6 is at 4th step ↑

7th jump J7 is at 7th step ↓

8th jump J8 is at 5th step ↑

9th jump J9 is at 8th step ↓

10th jump J10 is at 6th step ↑

11th jump J11 is at9th step ↓ (Water level)

Hence the required number of jumps = 11.

ii) Monkey’s position after the

NCERT Solutions for Class 7 Maths Chapter 1 Integers 6

1st jump J1 is at 5th step ↑

2nd jump J2 is at 7th step ↓

3rd jump J3 is at 3rd step ↑

4th jump J4 is at 5th step ↓

5th jump J5 is at 1st step ↑

Hence, the required number of jumps = 5.

iii)a) -3+2-3+2-3+2-3+2-3+2-3=-8

b) 4-2+4-2+4=8