1, A sample of 400 grams of radioactive substance decays according to the functionA(t)=400e^-0.025twhere t is the time in years. How much of the substance will be left in the sample after 20 years? Round your answer to the nearest whole gram.

243 g

33 g

1 g

0 g

2, How long will it take a sample of radioactive substance to decay to half of its original amount, if it decays according to the function A(t) = 350e^-0.169t, where t is the time in years? Round your answer to the nearest hundredth year.

34.66 yr

38.76 yr

4.10 yr

59.15 yr

3,What is the range of the function y =[1/3]^x?

(0, )

[0, )

(-, )

(-, 0)