Question

sum of the digits of a two digit number is 9 the number is 6 times the unit digit find the number

Answer 1

HI!!!

the sum of the digits=9

and the number itself is 6 times the unit digit

but we know that a unit digit cannot exceed 9

So,

6*1= 6 wrong

6*2=12 wrong

but 6*6=36 fulfills all conditions

3+6=9

and the no. is 6 times the unit

cheers

callio

Answer 2

Set t = the tens digit

u = the unitis digit

t + u = 9

Solve for t by adding -u to each side.

t = 9 - u

The value of the number is 10t + u.

(10t + u) = 6u

Substitute (9 - u) for t in the above

10(9 - u) + u = 6u

90 - 10u + u = 6u

 

90 - 9u = 6u

add 9u to each side

90 = 15u

divide each side by 15

6 = u

since t+u = 9

t + 6 = 9

add -6 to each side

t = 3

Since t+u = 9, 3+u = 9 and u = 6

So our number is 36