A) 9
B) 3
C) 6
D) 15
Correct Answer: C
Solution :
\[\frac{({{n}_{2}}-{{n}_{1}})({{n}_{2}}-{{n}_{1}}+1)}{2}\] Here, \[{{n}_{2}}=4,\,{{n}_{1}}=1.\] So \[(N)=\frac{(4-1)(4-1+1)}{2}\] \[=\frac{3\times 4}{2}=6.\] Hence, the correct option is [c].You need to login to perform this action.
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