Multiple choice

In what ratio should a $20\%$ methyl alcohol solution be mixed with a $50\%$ methyl alcohol solution, so that the resultant solution has $40\%$ methyl alcohol in it?

  1. $2:1$
  2. $1:2$
  3. $2:3$
  4. $3:2$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Using the alligation rule, the difference between the concentrations is |50 - 40| = 10 and |20 - 40| = 20. The ratio of the 20% solution to the 50% solution is 10:20, which simplifies to 1:2.

AI explanation

Use the method of alligation to find the mixing ratio for the two solutions. Subtract the 20 percent concentration from the desired 40 percent to get 20 parts of the stronger solution, and subtract the desired 40 percent from the 50 percent concentration to get 10 parts of the weaker solution. This ratio of weaker to stronger is 20 to 10, or 2:1, meaning the correct mixing ratio of the 20 percent solution to the 50 percent solution is 1:2.

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