Suppose two students need to prepare three solutions, each one-half as concentrated as the previous, from a stock solution. (a) One student dilutes 10 mL stock solution to a final volume of 20 mL. S/he dilutes 10 mL stock solution to a final volume of 40 mL. S/he dilutes 10 mL stock solution to a final volume of 60 mL. Does s/he have the solutions at the concentrations desired

Explanation:

When a solution is diluted ,its strength is decreased according to following

formula

S₁V₁ =S₂V₂

So when volume is doubled , strength becomes half .  One student dilutes 10 mL stock solution to a final volume of 20 mL. Its strength becomes half .

When S/he dilutes 10 mL stock solution to a final volume of 60 mL. ,

strength becomes 1/6 times .

So the first two experiment gives three solution  each one-half as concentrated as the previous .

beta decay is the answer