Researchers evaluate a sample of Carbon6 which has a halflif

Researchers evaluate a sample of Carbon-6, which has a half-life of 20 minutes. For a particular sample, they observed that 75% of the original amount of Carbon-6 had decayed. How old is this sample?

Solution

half life of carlbon is 20 min

half life means time required for 50% of the product to decay

therfore fot 75% to decay it requires 2 half times

because after 50 % complition 50 % is remained

in the next half times 25% is decayed they add up to give (75%) decay

therefore 2 half times = 2*20 = 40 min