Question

If the mean of marks of 25 boys of a class is 42 and the
mean of marks of 15 girls of the same class is 54. Then
the combined mean of whole class is
OPTIONS
46.5
b.
46
45
44​

Answer 1

Step-by-step explanation:

$mean = average$

also

$average =\dfrac{sum \: of \: quantity}{number \: of \: quantiy}$

according to above formulae

$\frac{sum \: of \: quantity }{quantity} = \frac{25 \times 42}{25} \\ \implies1050 marks\div 25students$

Accordingly Marks Of Girls=

$\frac{sum \: of \: quantity }{quantity} = \frac{15 \times 54}{15} \\ \implies810 marks\div 15students$

So

Total marks of girls and boys=

$1050 + 810 = 1860$

Total students =

$40$

Mean mark of whole class =

$1860 \div 40 = 46.5$