Question

There are 10 people in a lift.
These 10 people have a mean weight of 79.2 kg.
3 of these people get out of the lift.
These 3 people have a mean weight of 68 kg.
Work out the mean weight of the 7 people left in the lift.

Answer 1

Answer:

84kg

Step-by-step explanation:

10*79.2kg=792kg   the weight of the 10 people

3*68kg=204kg   the weight of the 3 people who get out of the lift

792kg-204kg=588kg   the weight of the 7 people left in the lift

so, the mean weight of the 7 people left in the lift=588kg:7=84 kg

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Answer 2

Given: There are 10 people in a lift. These 10 people have a mean weight of 79.2 kg. 3 of these people get out of the lift. These 3 people have a mean weight of 68 kg.

To find: The mean weight of the 7 people left in the lift.

Solution:

• The mean of a certain number of values is given by the formula,

        $Mean = \frac{Sum}{n}$

• Here, n is the number of inputs or the number of values entered.

• The sum of the weights of the 10 people in the lift is calculated as,

        $79.2 kg = \frac{(Sum)_{10} }{10}$

        $(Sum)_{10} = 792kg$

• The sum of the weights of the 3 people that got out of the lift is calculated as,

         $68 kg = \frac{(Sum)_{3} }{3}$

         $(Sum)_{3} = 204kg$

• Now, the sum of 7 people remaining in the lift is calculated as,

         $(Sum)_{7} = (Sum)_{10} - (Sum)_{3}$

                      $= 792-204$

                      $= 588kg$

• So, the mean of the weights of these 7 people is calculated as,

       $Mean = \frac{588}{7}$

                  $= 84kg$

Therefore, the mean weight of the 7 people left in the lift is 84 kg.