# In a certain test ai students gave wrong answers to atleast i questions, where i= 1,2,3......k No student gave more than k wrong answers.

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In a certain test ai students gave wrong answers to atleast i questions, where i= 1,2,3......k No student gave more than k wrong answers. The total number of wrong answers is _______

(a) a1+a2+... + ak

(b) a1+2a2+... +kak

(c) a1+a2+... + ak -k

(d) k/2(k+1)

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Correct option: (a) a1+a2+... + ak

Explanation:

Number of students gave i or more than i wrong answers = ai

Number of students gave i + 1 wrong answers = ai + 1

Number of students gave i wrong answers

= ai - ai + 1