Question

In order to get a certain shade of blue paint, a mixer must have 5 parts white paint to 3 parts blue. If 4 gallons of paint must be mixed, how many gallons of white paint must be used?
3.7 gallons
2.5 gallons
1.9 gallons
1.5 gallons

Answer 1

Answer:

Option B. 2.5 gallons of white paint must be used

Step-by-step explanation:

In order to get a certain shade of blue paint, a mixer must have 5 parts white paint to 3 parts blue.

Total paint was mixed = 4 gallons.

5 parts white + 3 parts blue = 8 parts

divide it into 8 parts to get each part must be  = 4 ÷ 8 = 0.5 gallons

It is given that 5 parts of white paint = 5 × 0.5 = 2.5 gallons

and 3 parts of blue paint was mixed = 3 × 0.5 = 1.5 gallons

Option B. 2.5 gallons of white paint must be used.

Answer 2

Answer: 2.5 gallons.

Step-by-step explanation:

Given : In order to get a certain shade of blue paint, a mixer must have 5 parts white paint to 3 parts blue.

Total paint mixed = 5+3= 8 parts

The ratio of white paint to the total mixture = $\dfrac{\text{Parts of white colour}}{\text{Total parts of mixture }}$

$=\dfrac{5}{8}$        (1)

Let x be the number of gallons of white paint.

If 4 gallons of paint must be mixed , then the  ratio of white paint to the total mixture = $=\dfrac{x}{4}$     (2)

From (1) and (2) , we have

$\dfrac{x}{4}=\dfrac{5}{8}$

Multiply 4 on both sides , we get

$x=\dfrac{5}{8}\times4=\dfrac{5}{2}=2.5$

⇒ x= 2.5

⇒ Number of gallons of white paint is required = 2.5 gallons.