Question

At Dorothy's Hair Salon, 4 gallons of shampoo will last 3 weeks. She has 7 gallons of shampoo. How much more must she order if she wants to have enough for 12 weeks?
I will give brainliest

Answer 1

Answer: 9 gallons

Step-by-step explanation:

We can see that the quantity of shampoo and the number of weeks a re directly proportional.

We know that if two quantities x and y are directly proportional , then we have the following equation :-

$\dfrac{x_1}{y_1}=\dfrac{x_2}{y_2}$

Let x be the total quantity of shampoo need for 12 weeks , then we have

$\dfrac{x}{12}=\dfrac{4}{3}\\\\\Rightarrow\ x = \dfrac{4\times12}{3}\\\\\Rightarrow\ x =16$

If she  has 7 gallons of shampoo, then the required quantity of shampoo for 12 weeks = $16-7=9$

Hence, she must order 9 gallons of shampoo if she wants to have enough for 12 weeks.

Answer 2

4 gallons=3 weeks
12 weeks/3 weeks = 4
4 gallons X 4 groups of 3= 16

Hope this helps....k