A water tank has capacity $4000$ litres. An starts pumping water into the empty tank at $20$ litres per minute. After $20$ minutes, the tank starts leaking at $2$ litres per minute. How many minutes after pumping begins will the tank be full?
Triangle $PQR$ is right-angled and isosceles at $Q$. The segments $QS,TU,VW$ are perpendicular to $PR$, and $ST,UV$ are perpendicular to $QR$, as shown. What fraction of the area of $PQR$ is shaded?
We have $2024=2^3\cdot11\cdot23$. Find the smallest natural number $A>2024$ that can be written as $A=p^3qr$, where $p,q,r$ are three distinct prime numbers.
An, Binh and Chau run a $200$ m race, and An finishes first. After $25$ seconds, the total distance covered by the three runners is $500$ m. When An finishes, the total distance Binh and Chau still have to run is $40$ m. How many seconds does An take to finish?
An and Binh start together from opposite vertices of a square of side $100$ m and walk anticlockwise along its perimeter. An walks at $50$ m/min and rests for $1$ minute whenever reaching a vertex. Binh walks at $40$ m/min and rests for $2$ minutes whenever reaching a vertex. After how many minutes do they first meet?
In the five-pointed star shown, the five interior angles of the central pentagon $FGHIJ$ are five consecutive integers in degrees. What is the largest possible value of one of the five tip angles $A,B,C,D,E$ of the star?