Question

Lydias hotel room number has three digits.The hundreds digit has a value of 40 Tens.The Tens digit is greater than 6. Which could be Lydias hotel room number?

Answer 1

Any 3 digit number can be expressed in the form of:

$(a*100)+(b*10)+(c*1)$

Where $a, b, c$ represent any natural number from 0 to 9.

We are told the hundreds number (this means $a*100$ in the expression above) is equal to the value of 40 tens, 40 tens is 400. Then, we know the digit in the tens is greater then 6, this means $b>6$ in the expression above.

So, there are multiple numbers the room number could be, namely:

$400+(b*10)+(c*1)$

where $b$ can be 7, 8, or 9; and $c$ can be  0, 1, 2, 3, 4, 5, 6, 7, 8, or 9. So, there's 30 possible room numbers Lydia may be.