Examples

Chapter 11 Class 8 Direct and Inverse Proportions
Serial order wise

### Transcript

Example 7 6 pipes are required to fill a tank in 1 hour 20 minutes. How long will it take if only 5 pipes of the same type are used? Let’s first convert time into minutes 1 hour 20 minutes = 1 hour + 20 minutes = 60 minutes + 20 minutes = 80 minutes It is given that 6 pipes fill tank in 80 minutes We need to find time taken if 5 pipes are used Let time taken be y minutes Thus, our table looks like As we increase the number of pipes, the time taken to fill the tank decreases ∴ Number of pipes and time taken are in inverse proportion 6 × 80 = 5 × 𝑦 (6 × 80)/5 = 𝑦 6 × 16 = 𝑦 96 = 𝑦 𝑦 = 96 minutes Converting to hours (𝑥1𝑦1=𝑥2𝑦2) 𝑦 = 96/60 hours 𝑦 = 1 hours 36 min ∴ 5 pipes will fill the tank in 96 minutes (1 hour 36 minutes)

#### Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 14 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.