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A small quantity of solution containing Na²⁴ radio nuclide (half life = 15 hour) of activity 1.0 microcurie is injected into the blood of a person. A sample of the blood of volume 1 cm³ taken after 5 hour shows an activity of 296 disintegerations per minute. Determine the total volume of the blood in the body of the person. Assume that radioactive solution mixes uniformly in the blood of the person. (1 curie = 3.7 x 10¹⁰ disintegerations per second)

Chemistry

In the reaction p-chlorotoluene with KNH₂ in liq. NH₃ , the major product is :

(a)	o-toluidine	(b)	m-toluidine
(c)	p-toluidine	(d)	p-chloroaniline

Mathematics

The mean square deviation of a set of observations x₁, x₂, ........, x_n about a points c is defined to be

The mean square deviations about -1 and +1 of a set of observations are 7 and 3 respectively. Find the standard deviation of this set of observations.