In the figure below, triangle $ABC$ is an isosceles triangle with $AB=AC$. Point $D$ is on $AC$ with $BD=BC$. If $\angle ABD=21^\circ$, what is the measure, in degrees, of $\angle BAC$?
Let $a$, $b$, $c$, $d$, $e$ and $f$ are distinct digits such that the expression $\overline{ab}+\overline{cd}=\overline{ef}$. What is the least possible value of $\overline{ef}$?
In the figure below, $AQBC$ is a convex quadrilateral with $QA=QB$ and $\angle C=60^\circ$. Triangle $QAB$ is folded along $AB$ to form triangle $PAB$. It is also known that $\angle PBC=30^\circ$ and $\angle PAC=20^\circ$. What is the measure, in degrees, of $\angle AQB$?
The length of 2 altitudes on adjacent sides of a parallelogram are 2 cm and 3 cm respectively with perimeter of the parallelogram is 18 cm. What is the area, in cm$^2$, of the parallelogram?
Three students are to participate in four games. Each student participates in at least one game and each game has exactly one student participating. In how many ways can this be done?
The sum of $a$, $b$ and $c$ is negative, while the product of these three numbers is positive. If $x=\frac{a}{|a|}+\frac{b}{|b|}+\frac{c}{|c|}$, what is the value of $x^{2017}-2017x^2+36$?
Tom starts working at 9:00 in the morning and finishes at 5:00 in the afternoon. How many more degrees does the minute hand rotates than the hour hand does on the clock during this period?
The price criteria of the subway ticket of a city is as follows: 2 dollars for within 4 km, 1 dollar more per 4 km for distances between 4 km and 12 km, 1 dollar more per 6 km for distances over 12 km. It costs 8 dollars to take subway from station A to station B. Which of the following is closest to the distance between A and B?
Consider a 3-digit number $\overline{abc}$, where $a$, $b$ and $c$ are distinct digits, so that their sum is 7. How many such three-digit numbers are there?
In the figure below, $ABCD$ is a quadrilateral where $AB=4$ cm, $BC=6$ cm, $CD=5$ cm, $DA=3$ cm and $\angle BAD=90^\circ$. Find the length, in cm, of $AC$.