MAHARASHTRA Class 10: Sum of First n Terms of an A.P. Videos | Determine terms of an arithmetic progression

S = 1 + 2 + 3 … + 48 + 49 + 50… (i)

S = 50 + 49 + 48 + … + 3 + 2 + 1 … (ii)

Adding (i) and (ii), we get

2S = 51 + 51 + 51 … (50 times)

∴ S = 50 × =25 × 51 = 1275 

Here, d = 3, a = 3

t₃₇ =?

We know that,

t_n = [a + (n -1)d]  

∴ t₃₇ = [a + (n -1)d]= [3 + (37 - 1)-3]= 111 

Here, a = 1 and d = 2