Solution of class 7 NCERT book chapter 1 exercise 1.1 questions no.10
Answers
Given: The question is: A water tank has steps inside it. A monkey is sitting on the topmost step. The water level is at the ninth step.
To find: (i) He jumps 3 steps down and then jumps back 2 steps up. In how many jumps will he reach the water level?
(ii) 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?
Solution:-
- Lets consider the steps moved down is represented by positive integers and steps moved up is represented by negative integers.
- Answer(i)
So, firstly monkey is sitting on the top step 1st step
On 1st jump he comes at step = 1 + 3 = 4 steps
On 2nd jump he comes at step = 4 + (-2) = 4 – 2 = 2 steps
On 3rd jump he comes at step = 2 + 3 = 5 steps
On 4th jump he comes at step = 5 + (-2) = 5 – 2 = 3 steps
On 5th jump he comes at step = 3 + 3 = 6 steps
- Similarly till 11 th jump monkey will be at step = 6 + 3 = 9 steps
Therefore, monkey takes 11 jumps (i.e., 9th step) to reach the water level.
- Answer(ii)
At start monkey is sitting on the ninth step,which is at the water level
On 1st jump he will be at step = 9 + (-4) = 9 – 4 = 5 steps
On 2nd jump he will be at step = 5 + 2 = 7 steps
On 3rd jump he will be at step = 7 + (-4) = 7 – 4 = 3 steps
On 4th jump he will be at step = 3 + 2 = 5 steps
On 5th jump he will be at step = 5 + (-4) = 5 – 4 = 1 step
Therefore, the monkey takes 5 jumps so as to reach back to the top step.
Answer:
For 1st, Monkey takes 11 jumps (i.e., 9th step) to reach the water level and for 2nd the monkey takes 5 jumps so as to reach back to the top step.
Answer:
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Step-by-step explanation:
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