1. ## Some math questions

pardon grammar.

1. The ratio of Boys to Girls in the Math class is 4:5 and the ratio of Boys to girls in the English class is 5:4. if there are 50 percent more females in the English class, what is the ratio of females in the math class to that of the English class?
2. 402 out of 500 times the a bottle cap fell bottom side up. If the same bottle cap is flipped twice, what is the probability that two of them will be bottom side up?
3. 150y^2 surface area of a cube. which is greater, volume of the same cube or 125y^3
4. Line making angle 48 degree with the x axis (slope negative, line trending downwards when moving from left to right) in the first quadrant, which is greater, sum of the coordinates of a point on the line or 0.
5. Standard deviation of a set of numbers is 16. if 10 more 16s are added will the SD change?  Reply With Quote

2. ## Re: Some math questions

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.  Reply With Quote