Numbers Flashcards
True or False: All Square and Cube roots of natural numbers that are not squares and cubes of natural numbers are irrational.
True
An odd number can be expressed in the form:
2n - 1
where n is a natural number
even + even =
even
odd + odd =
even
odd + even =
odd
even*even =
even
even*odd =
even
odd*odd =
odd
even^even =
even
odd^odd =
odd
even^odd =
even
odd^even =
odd
A number is divisible by 2, when its last digit is divisble by 2 or 0.
True
A number is divisible by 3, when the sum of its digits is divisible by 3.
True
e.g. 675, 160791
A number is divisible by 4 when the number formed by the last two digits is divisible by 4, or if they are 0.
True
7564, 6600
A number is divisible by 5 when its last digit is 5 or 0.
True
e.g. 245, 50
A number is divisible by 6, when it is divisible by 2 and 3 at the same time.
True
e.g. 354
A number is divisible by 7 if the number of tens added to five times the number of units is divisible by 7.
True
e.g. 364 Number of tens 36, 5 times the number of units = 5*4 = 20, 36 + 20 = 56 is divisible by 7, so 364 is divisible by 7
A number is divisible by 8 when the number formed by the last three digits is divisible is divisible by 8, or if they are 0.
True
e.g. 1000, 45677432
A number is divisible by 9 when the sum of its digits is divisible by 9.
True
e.g. 432657
A number is divisible by 10 when its last digit is 0.
True
e.g. 3480, 4870
A number is divisible by 11 when the difference between the sum of the digits in the odd and even places is 0 or a multiple of 11.
True
A number is divisible by 12 when it is divisible by both 3 and 4.
True
e.g. 252
A number is divisible by 13 if the number of tens added to four times the number of units is divisible by 13.
True
e.g. 1248 Number of tens = 124, Four times number of units = 4*8 = 32. 124 + 32 = 156 which is divisible by 13. Therefore 1248 is also divisible by 13.
