What is the 7th term?

Algebra Level 1

What is the seventh term of the arithmetic progression 2 , 7 , 12 , 17 , 2, 7, 12, 17, \dots ?


The answer is 32.

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5 solutions

Shazia Firdous
Feb 27, 2020

nth term is 7 and initial number is 2 and common difference in sequence is 5,so we know the formula tn=a1+d(n-1) Put the value in this, t7=2+5(7-1)=32 t7=32

Lisa Liu
May 17, 2021

Common difference is 5 5 .

2 + 6 ( 5 ) = 32 2+6(5)=\boxed{32}

Qian Chen
Mar 30, 2021

Look at it in pairs. _2 is always odd so 7th is _2. 1&2, 3&4 share the tens digit, so 7&8 also share the tens digit. The tens digit is the 2nd number in a pair divide by 2 and minus 1. Therefore, the answer is 7.

Darien Pérez
Jan 23, 2021

We have that: a n = a 1 + d ( n 1 ) a_{n} = a_{1} + d(n - 1)


  • To get a 1 a_{1} , we just choose the first number of our series, that in 2 , 7 , 12 , 17 , . . . 2, 7, 12, 17,... , is 2 2 .

    So, we get that a 1 = 2 a_{1} = 2


  • Then, to get d d , we could calculate the difference of two consecutive numbers using the formula ( a n + 1 a n ) (a_{n+1} - a_{n}) .

    For example: ( 7 2 = 5 ) (7 - 2 = 5) , and if we want to corroborate, we could just repeat it with some different consecutive numbers, like ( 12 7 = 5 ) (12 - 7 = 5) or ( 17 12 = 5 ) (17 - 12 = 5) .

    So, we get that d = 5 d = 5


  • Finally, to get n n , we just check the text, and it says that we need to know the seventh term.

    So, we get that n = 7 n = 7


Now, we can substitute on our main formula:

a n = a 1 + d ( n 1 ) a n = 2 + 5 ( 7 1 ) a n = 2 + 30 a n = 32 \\a_{n} = a_{1} + d(n - 1)\\ a_{n} = 2 + 5(7 - 1)\\ a_{n} = 2 + 30\\ \boxed{a_{n} = 32}

Parth Sankhe
Oct 19, 2018

The nth term of an arithmetic progression is:-

t n = a + ( n 1 ) d t_{n}=a+(n-1)d where a is the first term, and d is the common difference.

Putting n=7, we get it as 32.

Shouldn't the answer be 22 as this equation has a linear progression?

Diyon John - 2 years, 5 months ago

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The answer would be 22 if the question asked for the 5th term, but it asked for the 7th term of this linar progression

Trenton Cadena - 1 year, 7 months ago

it was helpful

Paul Gz - 3 months, 2 weeks ago

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