M4maths Previous Puzzles

30 Apr 2019 Number

A two digit number is 4 times to its sum of digits. When 18 is added to the number, the digits will get reversed. Then what is that number?

OPtion

1) 36
2) 48
3) 12
4) 42
5) 60
6) 72
7) 18
8) 24
9) 27
10) None of these

Solution

Let the 2 digit number be yx
When 18 is added digits are reversed.
(10x+y)-(10y+x)=18
solving we get x-y=-2
There are so many possibilities of different values of x,y vix
(1,3),(2,4)(3,5),(4,6)(5,7),(6,8),(7,9)
But from the above possibilities, the condition satsfies is the number 24
2+4 = 6
=> 6*4 = 24

Correct Option: 8 Best Solution (5)

G.S.Kantharao   6 years AGO

Let X,y are digits
10x+y=4(X+y)=>6x-3y=0
10x+y+18=10y+X=>9x-9y=-18
X=2,y=4
Number is 24
Right option is 8👈

Like? Yes (1) | No (1)  

RAMADURAI NATESAN   6 years AGO

Let the 2 digit no.be 10a+b.It is given that,
10a+b = 4(a+b) 0r b=2a.Further,
10a+b+18 = 10b+a ,or b - a =2. i.e, 2a-a=2 or a=2.
Hence b=4. the no.is 24.

Like? Yes (1) | No (1)  

Bharath Babu   6 years AGO

ab=4(a+b)
10a+b=4a+4b
b=2a --------------(1)

10b+a=10a+b+18
from (1) 20a+a=10a+2a+18
21a=12a+18
a=2;
b=4
ab=24

Like? Yes | No (1)  

Vignesh   6 years AGO

2+4=6; 6*4=24
24+18 = 42

Like? Yes | No (1)  

Dimple   6 years AGO

24 = 4*(2+4)
24+18=42

Like? Yes | No (1)