Q.

The sum of the common terms of the following three arithmetic progressions 3, 7, 11, 15, ...., 399; 2, 5, 8, 11, ...., 359 and 2, 7, 12, 17, ...., 197, is equal to ______.


Ans.

(321)

3, 7, 11, 15, …, 399 are in A.P.

So, common difference d1=7-3=4

2, 5, 8, 11, …, 359 are in A.P.

Then, d2=5-2=3;  2, 7, 12, 17, …, 197 are in A.P.

d3=7-2=5

L.C.M. of d1,d2,d3=L.C.M. of (4,3,5)=60

On expanding all A.P.s, common terms are 47, 107, 167

∴  Sum=47+107+167=321