Question

The half-life of a radioactive kind of tellurium is 25 minutes. If you start with 88 grams of it, how much will be left after 50 minutes?

Answer 1

Notice that 50 minutes is twice the half-life.

After 25 minutes, half of the starting amount remains, so that 88g decays to 44g.

After another 25 minutes (a total of 50 minutes), the 44g will decay to 22g.