It will take 5.2 years to decay.
The half life of cobalt-60 is 5.2 years. The half life is the time taken for the mass of the substance to decrease by a half.
here, the amount of remaining substance is 50%,
so, 
n. log (0.5) = log (0.5)
n = 1
So it would take 1 half lives to decay this much, which is 1 x 5.2 which is 5.2 years.
what do you mean by radioactive decay ?
The process through which an unstable atomic nucleus loses energy via radiation is known as radioactive decay, also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration. A material that has unstable nuclei is considered as radioactive.
Learn more about decay here:-
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Answer:
0.136g
Explanation:
A student dissolved 5.00 g of Co(NO3)2 in enough water to make 100. mL of stock solution. He took 4.00 mL of the stock solution and then diluted it with water to give 275. mL of a final solution. How many grams of NO3- ion are there in the final solution?

Initial mole of Co(NO3)2 

Mole of Co(NO3)2 in final solution

Mole of NO3- in final solution = 2 x Mole of Co(NO3)2

Mass of NO3- in final solution is mole x Molar mass of NO3

Answer:
More oxygen is needed to produce more energy, and more carbon dioxide waste must be removed from the body.
Explanation:
Oxygen helps our cells work harder by breaking down the nutrients we get from food like sugars. With sugars and oxygen, our cells can create the energy they need to function. This process also produces carbon dioxide. The carbon dioxide produced is a waste product and needs to be removed. During exercise, your body needs more energy, which means your tissues consume more oxygen than they do at rest. Consuming more oxygen means you will also produce more carbon dioxide because your metabolic rate is elevated. The lungs and respiratory system allow oxygen in the air to be taken into the body, while also letting the body get rid of carbon dioxide in the air breathed out. When you breathe in, the diaphragm moves downward toward the abdomen, and the rib muscles pull the ribs upward and outward.
This is a heterogeneous mixture.