Topic Included: | Formulas, Definitions & Exmaples. |

Main Topic: | Quantitative Aptitude. |

Quantitative Aptitude Sub-topic: | Time and Work Aptitude Notes & Questions. |

Questions for practice: | 10 Questions & Answers with Solutions. |

If there are two groups of workers \(x\) and \(y\). The group \(x\) is working to complete a task, where as group \(y\) is woking to destroy the task.

Here group \(x\) is doing positive work and group \(y\) is doing Negative work, then task will be completed $$ \left[Work \ of \ group \ x - Work \ of \ group \ y\right] $$

**Note:** We can also use this concept in the cases of Pipes and Cistern (Tank), discussed in the next chapter.

**Example (1):** \(P\) can finish a task in \(5 \ days\), where as \(Q\) can destroy the same task in \(10 \ days\). If they start working at the same time then how many days it will take to complete the task.

**Solution:** \(P\) can finish a task in \(5 \ days\), so in one day \(P\) can finish \(\frac{1}{5}\) part of the task.

\(Q\) can destroy the task in \(10 \ days\), so in one day \(Q\) can destroy \(\frac{1}{10}\) part of the task, then $$ \left[Work \ of \ P - Work \ of \ Q\right] $$ $$ \left[\frac{1}{5} - \frac{1}{10}\right] $$ $$ \left[\frac{2 - 1}{10}\right] = \frac{1}{10} $$

Hence task will be finish in \(10 \ days\).

**Example (2):** \(Jack\) can finish a task in \(20 \ days\), where as \(Johnson\) can destroy the same task in \(25 \ days\). If they start working at the same time then how many days it will take to complete the task.

**Solution:** \(Jack\) can finish a task in \(20 \ days\), so in one day \(Jack\) can finish \(\frac{1}{20}\) part of the task.

\(Johnson\) can destroy the task in \(25 \ days\), so in one day \(Johnson\) can destroy \(\frac{1}{25}\) part of the task, then $$ \left[Work \ of \ Jack - Work \ of \ Johnson\right] $$ $$ \left[\frac{1}{20} - \frac{1}{25}\right] $$ $$ \left[\frac{5 - 4}{100}\right] = \frac{1}{100} $$

Hence task will be finish in \(100 \ days\).

Lec 1: Time and Work Case (1) and Case (2)
Exercise-1
Lec 2: Time and Work Case (3) and Case (4)
Exercise-2
Lec 3: Concept of Positive and Negative work
Exercise-3
Lec 4: Concept of Pipes and Cisterns
Exercise-4
Lec 5: Concept of Efficiency
Exercise-5