First slide

Arithmetic progression

Question

The 10th common term between the series 3+7+11+.. and 1+6+11+… is

Moderate

A

191
B

193
C

219
D

198

Solution

The common differences of the two series are 4 and 5 respectively.
The series of common terms will form an A.P with common difference 20 and first term 11. ( l.c.m of 4 and 5 is 20 , which is the common difference of the required A.P)
$T_{10} =a+(n-1)d=11+(10-1) \times 20=191$

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