Latest TCS Aptitude Question SOLUTION: Two decks of cards are there. Each deck contains 20 cards, with numbers from 1 to 20 written on them. A card is drawn of random from each deck, getting the numbers x and y What

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(#M40153638) TCS Numerical Ability question probability Keep an EYE

Two decks of cards are there. Each deck contains 20 cards, with numbers from 1 to 20 written on them. A card is drawn of random from each deck, getting the numbers x and y What is the probability that log x + log y is a positive integer. Logs are taken to the base 10.
options:
a. 3/200
b. 29/200
c. 7/400
d. 1/50

Asked In TCS Garima Srivastava (8 years ago)

Unsolved Read Solution (3)

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Sreetama Dam  (8 years ago)

log x+log y=log(xy)
log (base 10)(xy) is integer when xy is 10^n,where n=1,2,3....so on
1. 10^1=10, 5*2--- 2 combinations or 10*1----2 combinations-------total 4 combinations
2. 10^2=100, 5*20---2 combinations or 10*10----1 combination-----total 3 combinations
all total 7 combinations are integers
total no of combinations possible=20*20
probabilility=7/(20*20)=7/400

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anandhi  (8 years ago)

Log x + log y = log(xy)
log xy is integer when (x,y) = (1, 10), (10, 1), (10, 10), (5, 20), (20, 5), (2, 5), (5, 2)
So required probability = 7/400

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S7  (8 years ago)

log x+log y=log(xy)
log (base 10)(xy) is integer when xy is 10^n,where n=1,2,3....so on
1- (10,1),(10,2),(10,3)...(10,9),(10,11).... upto 20. so total 19 combinations
2- (20,1),(20,2),(20,3)...(20,19), so total 19 combinations
3-(5,even numbers upto 20)=10 combinations
4-(15,even numbers upto 20_=10 combinaions
so total 58 combination.
so 58/400=29/200
m/

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