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Find the first term of an AP whose 8th and 12th terms are respectively 39 and 59.
- a)5
- b)6
- c)4
- d)3
- e)7
Correct answer is 'C'. Can you explain this answer?
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Verified Answer
Find the first term of an AP whose 8th and 12th terms are respectively...
Solution: 1st Method:
8th term = a+7d = 39 ........... (i)
12th term = a+11d = 59 ........... (ii)
(i)-(ii);
Or, a+7d-a-11d = 39-59; Or, 4d = 20;
Or, d = 5;
Hence, a+7*5 = 39;
Thus, a = 39-35 = 4.
2nd Method (Thought Process):
8th term = 39;
And, 12th term = 59;
Here, we see that 20 is added to 8th term 39 to get 12th term 59 i.e. 4 times the common difference is added to 39.
So, CD = 20/4 = 5.
Hence, 7 times CD is added to 1st term to get 39. That means 4 is the 1st term of the AP.
8th term = a+7d = 39 ........... (i)
12th term = a+11d = 59 ........... (ii)
(i)-(ii);
Or, a+7d-a-11d = 39-59; Or, 4d = 20;
Or, d = 5;
Hence, a+7*5 = 39;
Thus, a = 39-35 = 4.
2nd Method (Thought Process):
8th term = 39;
And, 12th term = 59;
Here, we see that 20 is added to 8th term 39 to get 12th term 59 i.e. 4 times the common difference is added to 39.
So, CD = 20/4 = 5.
Hence, 7 times CD is added to 1st term to get 39. That means 4 is the 1st term of the AP.
Most Upvoted Answer
Find the first term of an AP whose 8th and 12th terms are respectively...
39=a+7d, 59=a+11d, on solving. 4d=20,so d=5,so 59=a+(11×5), 59=a+55,so a=4.
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Community Answer
Find the first term of an AP whose 8th and 12th terms are respectively...
T8= a +( n-1)d, 39= a + 7d. similarly . 59= a+11d by solving this we get d= 5 ,a= 4 where a is first term and d be the common difference.
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Find the first term of an AP whose 8th and 12th terms are respectively 39 and 59.a)5b)6c)4d)3e)7Correct answer is 'C'. Can you explain this answer?
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Find the first term of an AP whose 8th and 12th terms are respectively 39 and 59.a)5b)6c)4d)3e)7Correct answer is 'C'. Can you explain this answer? for Quant 2024 is part of Quant preparation. The Question and answers have been prepared according to the Quant exam syllabus. Information about Find the first term of an AP whose 8th and 12th terms are respectively 39 and 59.a)5b)6c)4d)3e)7Correct answer is 'C'. Can you explain this answer? covers all topics & solutions for Quant 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for Find the first term of an AP whose 8th and 12th terms are respectively 39 and 59.a)5b)6c)4d)3e)7Correct answer is 'C'. Can you explain this answer?.
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