7 There are 10 boys and 20 girls in a class. The class has a test. The mean mark for all the class is 60 The mean mark for the girls is 54 Work out the mean mark for the boys

Please show working out!

Guest Oct 14, 2018

#1**+2 **

\(total_{all} = (n_{boys}+n_{girls})m_{total} = (10+20)60 = 1800 \\ total_{girls} = n_{girls}m_{girls} = 20 \times 54 = 1080 \\ total_{boys} = total_{all}-total_{girls} = 1800 - 1080 = 720\\ m_{boys} = \dfrac{total_{boys}}{n_{boys}}= \dfrac{720}{10}=72\)

kind of a sexist problem :P

Rom Oct 14, 2018

#1**+2 **

Best Answer

\(total_{all} = (n_{boys}+n_{girls})m_{total} = (10+20)60 = 1800 \\ total_{girls} = n_{girls}m_{girls} = 20 \times 54 = 1080 \\ total_{boys} = total_{all}-total_{girls} = 1800 - 1080 = 720\\ m_{boys} = \dfrac{total_{boys}}{n_{boys}}= \dfrac{720}{10}=72\)

kind of a sexist problem :P

Rom Oct 14, 2018