The ratio of girls to boys in class is 9 to 7 and there are 80 students in the class. how many girls are in the class?

Given that, the ratio of girls to boys in class is 9 to 7.

Let's assume there is 9x girls and 7x boys in the class.

There is total of 80 students which means sum of 9x and 7x must be equal to 80. So, we can set up an equation as following:

9x + 7x = 80

16x = 80 Combine the like terms.

Divide each sides by 16 to isolate x.

So, x = 5

Since there is 9x girls in the class. So, next step is to substitute x=5 in 9x to get the number of girls in the class. Therefore,

9x = 9(5) =45.

Hence, there is 45 girls in the class.

x = ±sqrt(10)

step-by-step explanation:

5 - 2x² = -15

subtract 5 from each side

5-5 - 2x² = -15-5

-2x^2   = -20

divide by -2 on each side

-2x^2   /-2= -20/-2

x^2 =10

take the square root on each side

sqrt(x^2 )=±sqrt(10)

x = ±sqrt(10)

check:

5 - 2x² = -15

+sqrt(10)

5 - 2(sqrt(10))² = -15

5 -2(10) = -15

5 -20 = -15

-15 = -15

-sqrt(10)

5 - 2(-sqrt(10))² = -15

5 -2(10) = -15

5 -20 = -15

-15 = -15

if you are looking for the unit rate then the answer would be 9 because unit rate is distance divided by time.

step-by-step explanation: