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A book contains $100$ pages. A page is chosen at random. What is the chance that the sum of the digits on the page is equal to $8$?

1. $0.08$
2. $0.09$
3. $0.90$
4. $0.10$

(1,7)(7,1)(2,6)(6,2)(3,5)(5,3)(4,4) and page number 8 itself are the total possible combinations.Shouldn't answer be 0.08
Why not

80 and 08 ??
Ohh....I forgot 80 :)

Note:- single digit page 8 can be written in 2 digit as 08.

the sum of two digits should be 8.

$x+y = 8, x1,x2>=0$

$C(n+r-1,r) = C(2+8-1,8)=C(9,8) =9$

Required probability = $\frac{9}{100} = 0.09$

Hence, (B) is the correct option!

Ans is 0.09 Right , But how you uses combination for this please explain?

@bhanu kumar 1 number of non negative integral solutions.

edited
Yes.Combinations are useful for larger values too.
chance that the sum of the digits on the page is equal to 8 are:-

8 ,17,26,35,44,53,62,71,80

so, ans= 9/100 = 0.09

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