JB Sequence Formulae Flashcards
1
Q
nth term in AP
A
a + (n-1)d
2
Q
sum of n terms in AP
A
(n/2) x (first term + last term)
or
(n/2) x (2a + [n-1]d)
3
Q
number of terms b/w 5 and 9
A
last - first - 1
= 9 - 5 -1
= 3
4
Q
number of terms b/w 5 and 9, inclusive
A
last - first + 1
= 9 - 5 + 1
= 5
5
Q
number of terms from 5 to 9
A
last - first + 1
= 9 - 5 + 1
= 5
6
Q
number of terms from 5 to 9, exclusive
A
last - first - 1
= 9 - 5 -1
= 3
7
Q
nth term in GP
A
a x r^(n-1)
8
Q
Sum of n terms in GP
A
a x ([1- r^n] / [1 - r])
9
Q
Sum of n terms in HP
A
(middle term) x n
