CBSE Class 7 Answered
An elevator descends into a mine shaft at the rate of 9 m per minute. If the descent starts from 20 m above the ground level how long will it take to reach -250 m?
Asked by Sikerwar_Indore | 18 Sep, 2018, 20:36: PM
If the descent starts from 20 m above the ground level how long will it take to reach -250 m?
The distance to be descended by the elevator = (-250) - (+20) = - 270 m
rate = ![begin mathsize 16px style fraction numerator distance space over denominator time end fraction
end style](https://images.topperlearning.com/topper/tinymce/cache/652164b9e1caaeeb6661f667d4870cc6.png)
![begin mathsize 16px style fraction numerator distance space over denominator time end fraction
end style](https://images.topperlearning.com/topper/tinymce/cache/652164b9e1caaeeb6661f667d4870cc6.png)
- 9 = (-270) ÷ x
Therefore x = (-270) ÷ (-9)= 30 minutes
Answered by Yasmeen Khan | 19 Sep, 2018, 14:56: PM
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