In the number series 4, 9, 19, 39, 79, the next term is _______. – UGC NET Question

The differences between successive terms are 5, 10, 20 and 40, each approximately doubling the previous difference. If this pattern continues, the next difference should be 80. Adding 80 to the last term 79 gives 159. Therefore, 159 is the correct next term in the sequence.

Option A:
Option A is 120, which gives a difference of 41 from 79 and does not align with the expected 80. This breaks the doubling behaviour of the differences. Hence, 120 is not correct.

Option B:
Option B is 140, implying a difference of 61, which again fails to match the predicted 80. It does not continue the simple doubling rule. Therefore, 140 cannot be accepted.

Option C:
Option C equals 159 and produces the new difference 80, following 5, 10, 20 and 40 in a clear doubling pattern. The extended differences 5, 10, 20, 40, 80 make the structure consistent. Thus, 159 is the valid continuation.

Option D:
Option D is 180, giving a difference of 101 from 79. That has no relation to the doubling sequence of differences and therefore breaks the pattern. So, 180 is not suitable.