Advertisements
Advertisements
Question
The nth term of an A.P. 5, 8, 11, 14,...... is 68. Find n = ?
Advertisements
Solution
The given A.P. is 5, 8, 11, 14,......
Here, a = 5, d = 8 – 5 = 3, tn = 68
Since tn = a + (n – 1)d,
68 = 5 + (n – 1)(3)
∴ 68 = 5 + 3n – 3
∴ 68 = 2 + 3n
∴ 66 = 3n
∴ n = `66/3`
∴ n = 22
APPEARS IN
RELATED QUESTIONS
If the 9th term of an A.P. is zero, then prove that 29th term is double of 19th term.
Find the sum of the following arithmetic series:
`7 + 10 1/2 + 14 + ... + 84`
Find the sum of the following arithmetic series:
(–5) + (–8) + (–11) + ... + (–230)
Decide whether the following sequence is an A.P., if so find the 20th term of the progression:
–12, –5, 2, 9, 16, 23, 30, ..............
Given Arithmetic Progression 12, 16, 20, 24, . . . Find the 24th term of this progression.
Find the 19th term of the following A.P.:
7, 13, 19, 25, ...
Find the 27th term of the following A.P.
9, 4, –1, –6, –11,...
Six year before, the age of mother was equal to the square of her son's age. Three year hence, her age will be thrice the age of her son then. Find the present ages of the mother and son.
For a given A.P. a = 3.5, d = 0, then tn = _______.
If the sum of first n terms of an AP is n2, then find its 10th term.
How many multiples of 4 lie between 10 and 205?
If third term and fifth term of an A.P. are 13 and 25 respectively, find its 7th term.
Find tn if a = 20 and d = 3.
How many two-digit numbers are divisible by 5?
Activity :- Two-digit numbers divisible by 5 are, 10, 15, 20, ......, 95.
Here, d = 5, therefore this sequence is an A.P.
Here, a = 10, d = 5, tn = 95, n = ?
tn = a + (n – 1) `square`
`square` = 10 + (n – 1) × 5
`square` = (n – 1) × 5
`square` = (n – 1)
Therefore n = `square`
There are `square` two-digit numbers divisible by 5.
12, 16, 20, 24,...... Find 25th term of this A.P.
Find a and b so that the numbers a, 7, b, 23 are in A.P.
In an A.P. if the sum of third and seventh term is zero. Find its 5th term.
Write the next two terms of the A.P.: `sqrt(27), sqrt(48), sqrt(75)`......
