What?

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Take a 2 digit number, divide it by 2, then multiply the result by 4, then subtract your original number from the result.

Is it the number you chose from the start?

yes can tell no

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8 solutions

Gusti Firmando
Aug 11, 2015

Let the number be x

(x/2 .4) - x = 2x - x = x

Uttkarsh Kohli
Aug 9, 2015

let the number be 14

divide it by 2 =7

multiply by 4=28

subtract the original number=28-14=14

hence the answer is YES.

PLEASE UPVOTE IF SATISFIED

@uttkarsh kohli You should not pick a particular number. You should provide a proof that is true for all 2-digit integers.

Noel Lo - 5 years, 10 months ago

@uttkarsh kohli Well ,are you really 20?

Abhijeet Verma - 5 years, 9 months ago

Don't you have more good question

Sonal Singh - 5 years, 9 months ago

Let the 2 2 -digit number be a b ab

According to the problem, the full expression is:

a b 2 × 4 a b = a b × 2 a b = a b ( 2 1 ) = a b \frac{ab}{2} \times{4}-ab= ab \times{2}-ab=ab (2-1)=ab

Hence, a b ab is the number we chose.

Tess Jennifer
Aug 24, 2015

Any 2 digit no. is written as, 10x+y.

so, (10x+y)(4/2) = 20x+2y

(20x+2y)-(10x+y)= 10x+y (Original No.)

Ashwini Kumar
Aug 31, 2015

let a no be y... y/2.4=2x..then..2x-x=x..

Prabir Mondal
Aug 23, 2015

Let the number be 18. Now if I divide by 2 it will be ( 18 /2=9). As per problem 9*4=36. Then subtract the number 18 from 36. It will be ( 36-18=18) e.g the starting number 18.

Riaz Abdulla
Aug 22, 2015

The fact that it is 2-digits is irrelevant and is intended to throw us off (x/2)•4 - x =2x - x = x

Alistair Bailey
Aug 22, 2015

This works for any number: (x/2)*4=2x, 2x-x=x

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