Paint containers

[neoreaves]

A certain shade of gray paint is obtained by mixing 3 parts of white paint with 5 parts of black paint. If 2 gallons of the mixture is needed and the individual colors can be purchased only in one-gallon or half- gallon cans, what is the least amount of paint, in gallons, that must be purchased in order to measure out the portions needed for the mixture?
(A) 2
(b) 2.5
(c) 3
(d) 3.5
(e) 4

[rajatmeh]

In 2 gallons of mixture
White paint required = 3*2/8=3/4 gallon ==> need to buy 1 gallon can
Black paint required = 5*2/8=5/4 gallon ==> need to buy 1 (1 gallon can) and 1(1/2 gallon can).

Total = 1 + 1 + 1/2 = 2.5 gallon

[genius_in_the_gene]

2.5 it is

[buskool]

2.5 it is.

[aaadith]

3x+5x=2
8x=2
x=0.25

white = 3x = 0.75 = 1*(1 gallon container)

black = 5x = 1.25 = 1 * (1 gallon container) + 1*(0.5 gallong container)

answer : 2.5 gallons

[gmat.760]

The parts of the white and black mixture is 3:5 so 3/8*2 gallons of white and 5/8 *2 gallons of black are required which is 0.75 and 1.25 respectively, since it is available only in 1/2 and 1 gallon you requie 1 gallon for white and 1.5 gallons for Black, so it is 2.5 gallons. Answer is B

[abhishek_mumbai]

make a ratio.. for every gallon.. we need 3/8 of white and 5/8 of black.
so for 2 gallons, we need 6/8 of white i.e. 3/4 gallon and 10/8 of black i.e. 5/4 gallons

now, as we can buy in 1 and 1/2 parts.. we need 1 gallon of white and 1.5 gallons of black.. total 2.5 gallons
we still have 1/4 gallon of white and 1/4 gallon of black remaining..
I'll see if I can use it for my store room (at least white)