Step 1: Background of demonetization in India
On 8th November 2016, the Government of India announced demonetization of high-value currency notes of ₹500 and ₹1000.
Step 2: Reason for demonetization
The move was aimed at curbing black money, counterfeit currency, and corruption. After this announcement, ₹1000 notes and old ₹500 notes ceased to be legal tender.
Step 3: Correct year
Thus, ₹1000 currency notes were declared invalid in the year 2016.
\[
\boxed{2016}
\]
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.