Question

if the ratio between 5th and 10th terms of an AP os 1:2 and 12th term is 36,find that AP

Answer 1

Answer:

3, 6, 9, 12, 15, 18, 21, 24, 27, 30...

Step-by-step explanation:

'n'th term in ap = a + (n-1)d

Thus, here, 5th term = a+4d

10th term = a+9d

12th term = a+11d

Given, (a+4d) / (a+9d) = 1/2

or, 2a + 8d = a + 9d

or, a = d

Also given, 12th term ⇒ a + 11d = 36

or, 12d = 36 [as a=d is proved previously]

or, d = 3

Thus, a = 3

Therefore, the ap: 3, 6, 9, 12, 15, 18...

Answer 2

Answer:

Step-by-step explanation:

5th term=a+4d

10th term=a+9d

12th term=a+11d

a+4d/a+9d=1/2

2a+8d=a+9d

a=d

Given that a+11d=36 or 12d=36

d=36/12

d=3, also a=3

A.P --»»» 3,6,9,12,15,............