John needs to mix a solution in the following ratio: 1 part

Alexandra needs to mix cleaning solution in the following ratio: 1 part bleach for every 4 parts water. When mixing the solution, Alexandra makes a mistake and mixes in half as much bleach as she ought to have. The total solution consists of 27 mL. How much bleach did Alexandra put into the solution?


A) 1.5
B) 3
C) 4.5
D) 5
E) 6

Could some please explain why answer is 3.
Thank you.

New ratio will become 1:8 (1:4 = 2:8; half of the bleach = 1:8) --> 1/9 of 27 = 3

hi
the ratio is 1:4..
but only half of sol is put...
so the actual ratio is 1/2:4 or 1:8..
so the quantity =1/9 * 27 =3
B

Similar question to practice: john-needs-to-mix-a-solution-in-the-following-ratio-1-part-144937.html

Only the names have been changed. Rest of the information is exactly the same.

Ratio needed is 1:4
But only half of the solution is mixed, hence actual ratio = (1/2):4 = 1:8

This means that the solution has total 9 parts, out of which I part if the bleach

Hence the quantity will be =1/9 * 27 =3. Option B

He was suppose to mix in the ratio of 1:4.
By mistake he mixed ½:4 or 1:8.
Therefore 1/(8+1) or 1/9 will be bleach.
Total solution is 27ml.
Therefore 1/9 of 27 = 3ml is the total bleach in it. Option D

We are given the following ratio:

bleach : water = x : 4x

Since only half of the bleach was used, the new ratio is 0.5x : 4x.
Since 27 mL were used, we can create the following equation to determine x:

0.5x + 4x = 27

4.5x = 27

x = 6

Since x = 6, John put 3 mL of bleach into the solution.

Answer: D

Hi All,

If you're not sure how to approach this question, then you can TEST THE ANSWERS and do a bit of easy 'brute force' math to get to the solution.

We're told that the ratio of bleach to water is SUPPOSED to be 1:4, but that John accidentally puts in HALF the bleach that he's supposed to and ends up with 27 mL of total solution. We're asked for the amount of bleach (in mL) that he actually put in.

Let's start with the smallest answer and work our way up...

Answer E: 1.5

IF.... John put in 1.5 mL of bleach....
then he should have put in 3 mL of bleach and 12 mL of water...
the total of THIS mixture is 1.5 + 12 = 13.5 mL which is TOO SMALL (notice that this total is exactly HALF of what it should be....)

Answer D: 3

IF.... John put in 3 mL of bleach....
then he should have put in 6 mL of bleach and 24 mL of water...
the total of THIS mixture is 3 + 24 = 27 mL which is an exact MATCH for what we were told, so this MUST be the answer.

Final Answer:

GMAT assassins aren't born, they're made,
Rich

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