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Seven digits from the numbers 1, 2, 3, 4, 5, 6, 7, 8 and 9 are written in random order. The probability that this seven digit numbers is divisible by 9 is : a. 7/9 b. 1/9 c. 2/9! d. 4/9 Please help me through the above problem. anyone please explain.

a+b=9 a^3 + b^3= 189 or, (a+b)^3-3ab(a+b)=189 or, ab=20 Now, a^2+b^2=(a+b)^2-2ab=81-40=41

Hello there!!!! Please help me through the below probability problem: There are 8 red balls, 5 green balls and 3 blue balls. Three balls randomly picked up without replacement. i) What is the probability that the third ball would be a blue one? ii) What is the probability that the 2nd ball would be either green or red ball?