Step 1: Understand pencil grading system
Pencils are graded based on hardness (H) and blackness (B):
- The more Hs (e.g., 2H, 4H), the harder the pencil and lighter the line.
- The more Bs (e.g., B, 2B, 4B), the softer the pencil and darker the line.
Step 2: Compare all options
- 2H: Hard pencil, makes lighter lines.
- 4H: Even harder than 2H, even lighter lines.
- H: Medium-hard pencil, still not very dark.
- 2B: Softer than H, makes a darker line.
\[ $\Rightarrow$ \text{Among all options, 2B is the darkest pencil.}
\]
\[
\boxed{\text{Correct Answer: (B) 2B}}
\]
Find the unknown frequency if 24 is the median of the following frequency distribution:
\[\begin{array}{|c|c|c|c|c|c|} \hline \text{Class-interval} & 0-10 & 10-20 & 20-30 & 30-40 & 40-50 \\ \hline \text{Frequency} & 5 & 25 & 25 & \text{$p$} & 7 \\ \hline \end{array}\]
Two concentric circles are of radii $8\ \text{cm}$ and $5\ \text{cm}$. Find the length of the chord of the larger circle which touches (is tangent to) the smaller circle.