Question

The 11th term and 21st term of an A.P are 10 & 29
respectively. Find.
i7 The first term and common difference.
ii>The 34th term, iii>n such that tn=55
​

Answer 1

First term ( a ) = ?

Common difference ( d ) = ?

11th term = 16

21st term = 29

Now,

 Nth term = First term + ( No. of terms - 1 )Common difference

11th term = a + ( 11 - 1 ) d

16 = a + 10d.

a = 16 - 10d    ----- ( 1 ).

Again,

Nth term = First term + ( No. of terms - 1 )Common difference

21st term = a + ( 21 - 1 )d

29 = a + 20d

29 - 20d = a  ------ ( 2 )

From ( 1 ) and ( 2 ), we get ,

29 - 20d = 16 - 10d

29 - 16 = 20d - 10d

13 = 10d

d = 13 / 10 = 1.3

By substituting the value of 'd' in ( 1 ),

a = 16 - 10d

a = 16 - 10 x

41st term = 3 + ( 41 - 1 ) 1.3

                = 3 + ( 40 ) 1.3

                = 3 + 52

                = 55

Answer 2

Answer:

41st term = 45

Explanation: