Let 
be the 20 marks of the boys, and 
be the 10 marks of the girls.
We know that the global mean was 70, meaning that
Multiplying both sides by 30 we deduce that the sum of the scores of the whole classroom is
By the same logic, we work with the marks of the boys alone: we know the average:
And we deduce the sum of the marks for the boys:
Which implies that the sum of the marks of the girls is 
And finally, the mean for the girls alone is
Answer:
Step-by-step explanation:
What problem?
Answer:
72 cupcakes
Step-by-step explanation:
Morgan can make 4 cupcakes with one cup of flour. She has 18 cups of flour and suppose she can make x cupcakes, then
1 cup of flour - 4 cupcakes
18 cups of flour - x cupcakes
Write a proportion:
Cross multiply:
Answer: A. Wed to Fri
We have a bunch of natural numbers and we're told a pair is in the ratio 2:5.
For natural numbers to have this ratio, the left number will be a multiple of two and the right number will be a multiple of five.
Our only option for a multiple of 5 is 15, Friday. So we have
2:5 = x:15
and x = 15*2/5 = 6
which was Wednesday's number. So we get Wed:Fri=6:15=2:5.
