CBSE Class 10 Answered
Given a.p. series is: 5,17,29,41.
Here, first term = a = 5 and common difference = d = 17 - 5 = 12
Now, we don't have to use the formula for nth term. So, the only way to solve it is by finding the 15th term by adding the common difference.:
Given, first term = a = 5
Second term = 17
Third term = 29
Fourth term = 41
Now, fifth term = 41 + 12 = 53
Sixth term = 53 + 12 = 65
Seventh term = 65 + 12 = 77
Eight term = 77 + 12 = 89
Ninth term = 89 + 12 = 101
Tenth term = 101 + 12 = 113
Eleventh term = 113 + 12 = 125
Twelvth term = 125 + 12 = 137
Thirteenth term = 137 + 12 = 149
Fourteenth term = 149 + 12 = 161
Fifteenth term = 161 + 12 = 173
Now, 240 more than fifteenth term = 173 + 240 = 413
Again, 240 ÷ 12 = 20
So, after 15 th term, 20 more terms are added to get the term which is 240 more than the 15 th term.
Hence, the required term = 15 + 20 = 35 th term