When the digits of a two digit number are interchanged then original number is greater than four time the new number so obtained. How many such natural numbers are there which satify the above given condition ?Ignore the numbers which have '0' in its unit place.

Options

A. 2
B. 3
C. 5
D. 6

Answer

B

Explanation

let the original number by xy
According to given condition
`(10x+y) gt 4(10y+x)`
`6x-39y gt 0`
On putting y=1
x has to be more than or equal to 7
So for y=1
Possible values for x are 7,8,9
So, 3 numbers are possible when y is 1
(71),(81),(91)
Values greater than 1 are not possible for y.
So there are 3 possible numbers.