$A$ can do a piece of work in $4 \, days$ and $B$ can do it in $12 \, days.$ In how many $days$ will they finish the work,both working together?

$A$ is $4$ times as fast as $B$ and is,therefore,able to complete a work in $45$ $days$ less than $B$. $A$ and $B$,working together,can complete the work in (in $days$)

Amit and Sujit together can complete a data entry assignment in $5$ days. Sujit's speed is $80\%$ of Amit's speed and the total key depressions in the assignment are $5,76,000$. What is Amit's speed in key depressions per hour if they work for $8$ hours a day?

Four examiners can examine a certain number of answer papers in $10 \, \text{days}$ by working for $5 \, \text{hours}$ a $\text{day}$. For how many $\text{hours}$ in a $\text{day}$ would $2$ examiners have to work in order to examine twice the number of answer papers in $20 \, \text{days}$? (in $\text{hours}$)

$A$ can do a piece of work in $20 \, \text{days}$ and $B$ in $30 \, \text{days}$. They work together for $7 \, \text{days}$ and then, both leave the work. Then, $C$ alone finishes the remaining work in $10 \, \text{days}$. In how many $\text{days}$ will $C$ finish the full work?

$A$ can do a piece of work in $8$ days. $A$ undertook it for $Rs. 320$. With the help of $B$,he finishes the work in $6$ days. $B$'s share is (in $Rs.$):