Question

needed with clear explanation​

Answer 1

Answer:

$final \: amount = initial( { \frac{1}{2} )}^{ \frac{t1}{t \: half} } \\ \frac{2}{3} = { (\frac{1}{2}) }^{ \frac{t1}{20} } ......eq1 \\ \frac{1}{3} = { (\frac{1}{2}) }^{ \frac{t2}{20} } .....eq2 \\ devide \: both \: the \: eq \\ we \: get... \\ { \frac{1}{2} }^{1} = { \frac{1}{2} }^{ \frac{t1 - t2}{20} } \\ so \: base \: are \: same \: \\ 1 = \frac{t1 - t2}{20} \\ t1 - t2 = 20$

hope the answer will help you

Answer 2

(B) 20min

Hope that help .

Best of luck for NEET!!!☺☺