[JEE Advanced 1982] a i students gave wrong answers to at least i questions i 1 k
$a_i$ students gave wrong answers to at least $i$ questions ($i=1,\dots,k$), none more than $k$. The total number of wrong answers given is ____
1 Answer
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· 4d ago
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Answer: $a_1+a_2+\cdots+a_k$.
A student with exactly $j$ wrong answers is counted in $a_1,\dots,a_j$, contributing $j$; summing over the layers gives total wrong $=\sum_{i=1}^k a_i$.
JEE Advanced 1982 · Permutations and Combinations — verified solution by the Vidaara Team.
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