Answer:
10, 11, 12, 13, 14, 15, 16, 17, 18, 19
Step-by-step explanation:
A two-digit number can be written as:
a*10 + b
Where a and b are single-digit numbers.
a is the tens digit
b is the units digit.
the reverse number is:
b*10 + a
We know that:
"If you add the digits together and multiply the result by 10, you will get 9 more than the reverse number"
Then:
(a + b)*10 = b*10 + a + 9
We now need to solve this for a and b, where the other restriction that we have is that a and b can be any whole number of the set {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}
Then:
(a + b)*10 = b*10 + a + 9
a*10 + b*10 = b*10 + a + 9
subtracting b*10 in both sides, we get:
a*10 = a + 9
solving this for a, we get:
a*10 - a = 9
a*(10 - 1) = 9
a*9 = 9
a = 9/9
a = 1
and notice that we do not have any restriction for b. So b can be any number of the set.
for example, if b = 2
a*10 + b = 12
now let's test the property:
10*(1 + 2) = 2*10 + 1 + 9
30 = 20 + 10 = 30
now if b = 4, we have:
a*10 + b = 1*10 + 4 = 14
10*(1 + 4) = 4*10 + 1 + 9
50 = 50
So we can see that for any value of b, this will work.
So the only restriction that we have, is that a must be equal to 1.
Then the numbers are:
10, 11, 12, 13, 14, 15, 16, 17, 18, 19
