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Which of the Following Sequences Are Arithmetic Progressions? for Those Which Are Arithmetic Progressions, Find Out the Common Difference. 12, 2, −8, −18, ... - Mathematics

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Question

Which of the following sequences are arithmetic progressions? For those which are arithmetic progressions, find out the common difference.

12, 2, −8, −18, ...

Solution

In the given problem, we are given various sequences.

We need to find out that the given sequences are an A.P or not and then find its common difference (d)

12, 2, −8, −18, ...

Here,

First term (a) = 12

`a_1 = 2`

`a_2 = -8`

Now, for the given to sequence to be an A.P,

Common difference (d) = `a_1 - a = a_2  - a_1`

Here

`a_1 - a = 2 - 12`

= - 10

Also

`a_2 - a = -8 - 2`

= - 10

Since `a_1 - a = a_2 - a_1`

Hence, the given sequence is an A.P with the common difference d = -10

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Chapter 5: Arithmetic Progression - Exercise 5.3 [Page 11]

APPEARS IN

RD Sharma Mathematics [English] Class 10
Chapter 5 Arithmetic Progression
Exercise 5.3 | Q 6.04 | Page 11

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Case Study

Push-ups are a fast and effective exercise for building strength. These are helpful in almost all sports including athletics. While the push-up primarily targets the muscles of the chest, arms, and shoulders, support required from other muscles helps in toning up the whole body.


Nitesh wants to participate in the push-up challenge. He can currently make 3000 push-ups in one hour. But he wants to achieve a target of 3900 push-ups in 1 hour for which he practices regularly. With each day of practice, he is able to make 5 more push-ups in one hour as compared to the previous day. If on first day of practice he makes 3000 push-ups and continues to practice regularly till his target is achieved. Keeping the above situation in mind answer the following questions:

  1. Form an A.P representing the number of push-ups per day and hence find the minimum number of days he needs to practice before the day his goal is accomplished?
  2. Find the total number of push-ups performed by Nitesh up to the day his goal is achieved.

If the terms 10, a, 40 are in A.P., then find the value of a.


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