How many terms are there in the AP 1
, 1 
, …., –16 
?
To Find: we need to find number of terms in the given AP.
Given: The series is 1
, 1
, …., –16 
.
a1=1
= 
, a2= 1
=
, d=(
)–(
)= 
and an= –16 
= 
(Where a=a1 is first term, a2 is second term, an is nth term and d is common difference of given AP)
Formula Used: an = a + (n - 1)d
an= 
= a1 + (n–1)(
)
– 
= (n–1)(
) [subtract 
on both sides]
= (n–1)(
) [Multiply both side by 
] or [Divide both side by 
]
27 = (n–1) [add 1 on both sides]
n =28
So there are 28 terms in this AP.
1