Find the 11th term from the end in the AP 56, 63, 70, ..., 329

Given sequence:

56, 63, 70, ..., 329

First find the common difference:

d=a2-a1

d=63-56

d=7

Formula:

an=a1 + (n-1) d

First find the number of terms.

329=56 + (n-1) 7

329=56+7n-7

329=49+7n

280=7n

40=n

or

n=40

We have to find 40-11=29 th term (11 th term from the end)

a29 = 56 + (29-1) 7

a29=56 + (28) 7

a29=56+196

a29=252

Answer: 252 is 11th term from the end.