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Mathematics · 2025 · 2 marks
CBSE 2025 · Region 6 · Set 1 · Q25
The number of red balls in a bag is three more than the number of black balls. If the probability of drawing a red ball at random from the given bag…
The number of red balls in a bag is three more than the number of black balls. If the probability of drawing a red ball at random from the given bag is $\displaystyle \frac{12}{23}$, find the total number of balls in the given bag.
Marking-scheme solution
Let number of black balls \(\displaystyle =x\) then number of red balls \(\displaystyle =x+3\)
∴ total number of balls \(\displaystyle =2 x+3\)
ATQ,
\[\begin{gathered}
\frac{x+3}{2 x+3}=\frac{12}{23} \\
x=33
\end{gathered}
\]
Total number of balls \(\displaystyle =69\)
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CBSE Class 10 Mathematics past-paper question from the 2025 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.