Play with N.

Algebra Level 2

Let N N be a natural number such that 999 < N < 9999 999<N<9999 . If its left-most digit is deleted, it gets reduced to N 29 \dfrac{N}{29} .

Find N N .


The answer is 7250.

This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try refreshing the page, (b) enabling javascript if it is disabled on your browser and, finally, (c) loading the non-javascript version of this page . We're sorry about the hassle.

1 solution

Hrithik Thakur
Oct 15, 2019

Let N N = abcd, where a,b,c,d are single digit whole numbers, and a>0.

So, we may write, N= 1 0 3 a + 1 0 2 b + 10 c + d 10^{3} a+\ 10^{2}b+10c+d .

Therefore, N 29 = 1 0 2 b + 10 c + d \frac{N}{29}= 10^{2}b+10c+d .

Now, from the two equations, we get, 1 0 3 a = 28 ( 1 0 2 b + 10 c + d ) 10^{3}a=28(10^{2}b+10c+d) So, 28 = 7 2 2 28=7*2^{2} is a factor of 1 0 3 a 10^{3}a , which means that 1 0 3 a 10^{3}a must contain a power of 7 in its prime factorisation.

So, a a has to be one among 7 , 14 , 21 , . . . 7,14,21,... . But, a a is a one-digit number, so only possible value of a is 7 a\text{ is 7} . After, putting a = 7 a=7 in the third equation, we get

100 b + 10 c + d = 250. 100b+10c+d=250.

Each of b,c and d is a one-digit number, so, their values are:

b = 2 , b=2, c = 5 , c=5, d = 0. d=0.

Hence, N N is 7250 7250 .

0 pending reports

×

Problem Loading...

Note Loading...

Set Loading...