Ex 13.2, 10 Two persons could fit new windows in a house in 3 days. (i) One of the persons fell ill before the work started. How long would the job take now?
Given,
2 person can fit the window in 3 days.
If one person fell ill,
then, only one person will do the job.
We need to find how long will it take to do the job
Let the time taken 𝑦 days
Thus, our table looks like
As we increase the number of persons,
the time taken to complete the job decreases
∴ They are in inverse proportion
2 × 3 = 1 × 𝑦
6 = 𝑦
𝑦 = 6
∴ 1 person will complete the job in 6 days.
Ex 13.2, 10 Two persons could fit new windows in a house in 3 days. (ii) How many persons would be needed to fit the windows in one day?
We need to find how many persons would fit the window in 1 day
Let number of persons be x
Thus, our table looks like
Since number of persons and time taken are in inverse proportion
2 × 3 = 𝑥 × 1
6 = 𝑥
𝑥 = 6
∴ 6 persons will fit the windows in 1 day.

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 13 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.

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