A travel mug of 87∘C coffee is left on the roof of a parked car on a cold winter day. The temperature of the coffee after t minutes is given by H=87(2)−t/14. After how many minutes will the coffee be only lukewarm (30∘C)?

After 21.28  minutes will the coffee be only lukewarm (30∘C)

Step-by-step explanation:

Given -

A travel mug of 87∘C coffee is left on the roof of a parked car on a cold winter day . The temperature of the coffee after t minutes is given by

Let after time  H will be C

put t =  ,  H = C

      .3448275 =

     Taking logarithm both side  

     [ ]

      log.3448275 = log 2

      -.4581  =  

         =  -1.52

        = 21.28 minutes