Question

A number of two digits is equal to four times the sum of the digits. If the product of the digits is 18. Find the numbers.

Answer 1

let "d" for the tens digit and "u" for the units digit.

The two-digit number is four times the sum of the digits:

10d + u = 4(d + u)

The product of the digits is 18:

d*u=18

to sum up :

10d + u = 4(d + u)=10d+u-4d-4u=6d-3u=2d-u

d*u=18

on a file system:

2d-u

from=18

--->3d=18

--->d=6

we calculate u:

from=18

6*u=18

u=18/6=3

pair of numbers sought (6,3)

verification :

sum of digits = 9

4 times the sum of the digits = 36

the number: 36