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← JEE Main 2026 · 6 Apr · Shift 2
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JEE Main 2026 · 6 Apr · Shift 2, Mathematics question 21

Let R={(x,y)∈N×N:log⁡e(x+y)≤2}R=\left\{(x,y)\in\mathbf N\times\mathbf N:\log_e(x+y)\le2\right\}. Then the minimum number of elements, required to be added in R to make it a transitive relation, is ________.

Answer and worked solution

Official answer: 15

R. log⁡e(x+y)≤2\log_e(x+y)\le2 means x+y≤e2≈7.39x+y\le e^2\approx7.39, so x+y≤7x+y\le7. That is ∑x=16(7−x)=21\sum_{x=1}^6(7-x)=21 pairs.

Transitive closure. For a,c≤6a,c\le6, (a,1)(a,1) and (1,c)(1,c) are in R, so (a,c)(a,c) must be added. The set {1,…,6}2\{1,\dots,6\}^2 (36 pairs) is transitive and contains R.

Added: 36−21=1536-21=15.

Answer: 15

Topics:Relations