Question

Number 17 please and thank you . I don’t understand it . Do you plug in each 10-50 as T into your calculator?

Answer 1

The half-life for such a substance is the time
`t` required to have the amount (in grams
`\mathrm g`) at time
`t` (in seconds
`\mathrm s`),
`y(t)`, decay to half the starting amount
`y_0`. In other words, for krypton-91, after 10 seconds we would have
`y(10\,\mathrm s)=\frac{y_0}2`. We can use this information to solve for
`k`, then plug in various values of
`t` to find the amount of krypton-91 that's left...

But we don't need to! We already know it takes 10 seconds for half of the substance to decay. So if we start with 16 grams, then after 10 seconds, 8 grams will remain.

10s later (after a total of 20 seconds), 4g will remain.

10s later (30s), 2g will remain.

10s later (40s), 1g will remain.

10s later (50s), 1/2 g will remain.