How many numbers from 11 to 50 are there which are exactly divisible by 7 but not by 3?
Five
Four
Six
Two
* * * * *
Good strategy! List all possible values and one of them must be correct! The correct answer is 4.
7, 14, 21, 28, 35, 42, 49, 56
There are nine numbers between 10 and 100 that are evenly divisible by 11.
11
All multiples of 605 are divisible by 605:605, 1210, 1815, 2420, 3025, ...The numbers that 605 is divisible by, ie the numbers that divide 605 exactly, are its factors which are: 1, 5, 11, 55, 121, 605
Just the one: 11 itself. If any other number were divisible by 11 that number would not be a prime.
12
9 of them.
7, 14, 21, 28, 35, 42, 49, 56
There are nine numbers between 10 and 100 that are evenly divisible by 11.
There are 6 numbers between 1 and 70 that are divisible by 11. These numbers are: 11; 22; 33; 44; 55; 66.
286 is divisible by 1, 2, 11, 13, 22, 26, 143 and 286. The numbers exactly divisible by x are called the factors of x.
11
8 of the numbers less than 660 are divisible by 5 and 11 but not 3. All numbers divisible by 5 and 11 are multiples of their lcm; lcm(5, 11) = 55 All numbers divisibile by 5, 11 and 3 are multiples of their lcm; lcm(5, 11, 3) = 165 659 ÷ 55 = 11 54/55 → 11 numbers less than 660 are divisible by 5 and 11 659 ÷ 165 = 3 164/165 → 3 numbers less than 660 are divisible by 5, 11 and 3 → of the 11 numbers less than 660 divisible by 5 and 11, 3 are also divisible by 3 → 11 - 3 = 8 numbers less than 660 are divisible by 5 and 11 but not 3,.
All multiples of 605 are divisible by 605:605, 1210, 1815, 2420, 3025, ...The numbers that 605 is divisible by, ie the numbers that divide 605 exactly, are its factors which are: 1, 5, 11, 55, 121, 605
There are 90 such numbers.
Just the one: 11 itself. If any other number were divisible by 11 that number would not be a prime.
90.