UPSC NDA I 2026 Mathematics Paper

Concept:Total outcomes are $6^4 = 1296$; count favourable outcomes where the sum is at least 23.Explanation:Maximum total with four dice is $6+6+6+6=24$.For total $24$: each die must show $6$. That gives $1$ outcome.For total $23$: three dice show $6$ and one die shows $5$. The die showing $5$ can be any of the four dice, giving $4$ outcomes.Total favourable outcomes $=1+4=5$.So required probability is $\frac{5}{1296}$.Answer:$\frac{5}{1296}$, i.e. option D.