CAT (QA) PYQs

A CAT aspirant appears for a certain number of tests. His average score increases by $1$ if the first $10$ tests are not considered, and decreases by $1$ if the last $10$ tests are not considered. If his average scores for the first $10$ and the last $10$ tests are $20$ and 30, respectively, then the total number of tests taken by him is

The arithmetic mean of $x, y$ and $z$ is $80$, and that of $x, y, z, u$ and $v$ is $75$, where $u=(x+y) / 2$ and $v=(y+z) / 2$. If $x \geq z$, then the minimum possible value of $x$ is

The average weight of students in a class increases by $600$ gm when some new students join the class. If the average weight of the new students is $3$ kg more than the average weight of the original students, then the ratio of the number of original students to the number of new students is