Mark the correct alternative in the following:
The 10th common term between the A.P.s 3, 7, 11, 15, ... and 1, 6, 11, 16, ... is
Here, common difference of first A.P. is d=7-3=4
And common difference of second A.P. is d’=6-1=5
Now L.C.M of d and d’=(4,5)=20
Also first common term in both A.P.s is 11.
We have to find 10th common term i.e. n=10
Consider an A.P. in which a=11,d=20 and n=10
Then, a10=a+(10-1)d
=11+9×20
=11+180
=191