A random sample of students were chosen from all of 7th grade. There were 3 boys and 5 girls in that sample. If there are a total of 240 students on campus, how many students might be boys?

90

Step-by-step explanation:

3 boys

5 girls,

Say that there where "x" number of groups like this, (x will be the total number of groups like this, if one were to divide the population by the number of groups, they would the number of students);

Set up an equation;

x ( 3 + 5 ) = 240

Combine like terms and distribute;

8x = 240

Inverse operations;

8x = 240

/8        /8

x = 30

Substitute back in to find the number of boys;

30 * 3 = 90

(a) the volume of the cone is 20/3 in3

hence, option a is correct.

a 4/6 = 9/12   not proportional

step-by-step explanation:

to find which are not proportional, we can use cross products

if it is true, they are proportional.   if it is not true, they are not proportional.

a 4/6 = 9/12

4* 12 = 6*9

48 = 54

not this is not proportional  

b 2/3 = 12/18  

2* 18 = 3 * 12

36 = 36

this is proportional

c 5/4 = 10/8  

5*8 = 4*10

40 = 40

this is proportional

d 7/5 = 35/25

7*25 = 5 * 35

175 = 175

is proportional