1.

Math class: G=50 B=40 >> B/G=4/5

Eng class: G=75(50+50%) B=5*75/4 >> B/G=5/4

G(math)/G(eng) = 2/3

we dont need the ratio of boys to girls.

*but if it said: ratio of B(eng)/B(math) we needed all ratios >> (5/4)^2*3/4

2.

question is not obvious. but we assume that : 402 out of 500 fell bottom >> p(bottom)=402/500 , p(up)=98/500

if flipped twice the probability that two of them will be bottom >> 402/500*402/500=0.646416

3.

if y=1>> S is greater, if y=2 V is greater. so >> D is answer.

4.

in the first quadrant both x,y are positive. if angle was 45 >> the growth of x and y was equal so in quadrant first,second,forth(line exist)>> all the time greater than 0

but for angle 48>> in quadrant first and second x+y>0, but in quadrant forth, growth of y (which is negative) is more than x, so x+y will be negative.

5.

the question is not obvious.

if 10+16SD is added, yes will change

if 10*16SD is added, i think it will change. the only time that SD doesnt change is when we add numbers equal to mean.