xmagedo wrote:
I need someone to explain the questions with datialed but thanks for the help anyway
you know S/T= 64 + .12
.12= R/T R/T=12/100 -> R/T=3/25 -> 25R = 3T , because 25 does not have any factors of 3 in it that means that R must have a factor of 3 in it because 25 x R = a multiple of 3. Try plugging in real numbers if this seems fuzzy.
The second one is a combinators problem. The only way you can get the answer is by counting the possibilties.
999-700 = 299 total numbers
at this point you can find the number of ways where two equal digit occurs for 3 digit numbers or you can find number of ways that two equal digits do not occur subtract it from the total number of possibilitys
There are 3 possibilities for the first number 7,8,9
There are 10 possibilities for the second 0-9
There are 10 possibilities for the third 0-9
A 3 digit number can be 1 of 3 things in this case. It can have no equal digits, It can have 1 equal digit or it can have 2 equal digits. For example a number can be 707, 770, or 777. The possibility of having only 2 equal digit is as Bunuel mentioned "
{all} - {all distinct} - {all same} = {two equal}}
All = 299
All Distinct = 3x9x8 ( 3 for the first choice, the pool of choices is reduced by 1 for the second number, the pool is reduced again for the third - because we want
DISTINCT numbers.
All same = 3 There only 3 numbers greater than 700 that are all the same here: they are 777,888, and 999
so - > 299-216-3=80.
You can solve this problem another way by finding directly how many numbers have 2 equal digits but its much harder.
_________________
Ps. Kudos are always welcomed ; )