Question 1120214
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Point M is chosen random inside the big circle The radii of the small, middle and big circles are 4 cm, 7 cm, 10 cm respectively. 
What is the probability that 
a. Point M will be in the part C ?
b. Point M will be in the part B ?
c. Point M will be in the part A ?

image here:
http://homework.russianschool.com/resource?key=52745jgxxhu6i
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<pre>
a. Point M will be in the part C ?     The probability = {{{the_area_of_the_circle_C/the_area_of_the_circle_A}}} = {{{(pi*4^2)/(pi*10^2)}}} = {{{16/100}}} = 0.16 = 16%

b. Point M will be in the part B ?     The probability = {{{the_area_of_the_circle_B/the_area_of_the_circle_A}}} = {{{(pi*7^2)/(pi*10^2)}}} = {{{49/100}}} = 0.49 = 49%.

c. Point M will be in the part A ?     The probability = 1 = 100%.
</pre>



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<U>Comment from student</U>: &nbsp;thank you for helping with problem a. &nbsp;however, i believe problem b & c are incorrect?
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<U>My responce</U>:  &nbsp;&nbsp;From my name &nbsp;(referring to me) &nbsp;say to the teachers in your school that they &nbsp;INACCURATELY&nbsp; formulate the problem.


The accurate formulation must say that  B  is the part of the middle circle which is not in &nbsp;A.  &nbsp;&nbsp;From your post, &nbsp;I read it differently.


Same for the part c.



I respect &nbsp;"Russian Math school"&nbsp; very much, &nbsp;but in this case they are not correct . . .