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  1. Chapter 1 Class 7 Integers
  2. Serial order wise
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Transcript

Ex 1.4, 5 The temperature at 12 noon was 10 C above zero. If it decreases at the rate of 2 C per hour until midnight, at what time would the temperature be 8 C below zero? What would be the temperature at mid-night? Temperature at 12pm = 10 C Temperature decreases at 2 C per hour We need to find Time when temperature is 8 C below zero, i.e., 8 C Total decrease = Final temperature Initial Temperature = 8 C 10 C = 8 10 = (8 + 10) = 18 C Now, Temperature decrease in 1 hour Total number of hours = Total decrease Total number of hours = ( )/( 1 ) = 8/12 = 9 So, in 9 hours, temperature becomes 8 C Temperature is 8 C at 9 PM Now, We need to find temperature at mid-night Temperature at 12 AM Temperature at 12 PM = Temperature change in 12 hours Temperature change in 1 hour = 2 C Temperature change in 12 hours = 2 12 C = 24 C Now, Temperature at 12 AM Temperature at 12 PM = Temperature change in 12 hours Temperature at 12 AM 10 C = 24 C Temperature at 12 AM = 24 + 10 C Temperature at 12 AM = (24 10) C Temperature at 12 AM = 14 C Temperature at mid-night = 14 C

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Davneet Singh
Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 8 years. He provides courses for Maths and Science at Teachoo. You can check his NCERT Solutions from Class 6 to 12.