Chapter 5: Arithmetic Progression

Nth term of AP 

a+(n-1) d

Where a. is first term d is common difference and n is number of terms 

Que find 5th term for series

2,4,6,8.......

a= 2.    d=4-2=2.   n = 5

T(5) = 2+(5-1)2

         = 2+4×2

         = 2+8=10

Sum of series 

S= n/2{2a+(n-1)d}

Find sum of series for 

3,6,9,12....... Up to 20 terms 

first term 3

common difference 6-3=3

number of terms n=20 

S = 20/2 {2×3+(20-1)×3}

    = 10 {6+19×3}

   = 10 × {6+57}

    = 630