In the laboratory, a student dilutes 13.8 mL of a 10.7 M perchloric acid solution to a total volume of 125.0 mL. What is the concentration of the diluted solution? Concentration= ___M​

Idont know. if you want an answer you need to give us some context dude.

Radon-222 or rn-222 has a half-life of 3.82 days. to determine the fraction of an original sample of rn-222 that remains unchanged after 7.646 days, we calculate the amount of rn-222 remaining after 7.646 days and divide it with the original amount. using 1 gram as a basis and using half-life calculation methods, we can determine that  0.249 or 0.25  grams of rn-222 will remain, and thus the fraction remaining is 0.25 or 1/4.