Question

The sum of the first 10 terms common to the series 17, 21, 25, …… and 16, 21, 26, ….. is

• A. 1100
• B. 1010
• C. 1110
• D. 1200

Answer 1

The correct option is C 1110

The first common term is 21. The common difference of the first series is 4. The common difference of the second series is 5. The common difference of the common is the L.C.M of 4 and 5, i.e., 20.
$\therefore$ The sum of first 10 common terms is $\frac{10}{2}[2\times 21+9\times 20]=1110$