Q68 of 84 Page 5

The 19th term of an A.P. is equal to three times its sixth term. If its 9th term is 19, find the A.P. (CBSE 2013)

Given: a9 =19

a + 8d= 19 (i)


Acc. to question,


a19= 3a6 (ii)


a19=a + 18d


a6=a + 5d


Putting the value of a19 and a6 in (ii)


a + 18d =3(a +5d)


3d= 2a


3d=2(19 -8d) (from (i))


19d=38


d=2


Now, putting the value of d in (i)


a=19 -8(2) =3


a1 = a=3


a2 =a +d=3 +2=5


a3 =a +2d=3 + 2(2)=7


Hence, the A.P. is

More from this chapter

All 84 →
66

The 24th term of an AP is twice its 10th term. Show that its 72nd term is 4 times its 15th term. (CBSE 2013)

 67

Find the number of terms of the AP - 12, - 9, - 6, ..., 21. If 1 is added to each term of this AP then find the sum of all terms of the AP thus obtained. (CBSE 2013)

 69

The 9th term of an A.P. is equal to 6 times its second term. If its 5th term is 22, find the A.P. (CBSE 2013)

 70

The sum of 5th and 9th terms of an AP is 30. If its 25th term is three times its 8th term, find the AP. (CBSE 2014)