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2.
An even prime
The only even prime number.
4.
Greatest possible difference between 2 of the numbers below
It would be 4 - 1 = 3
5.
Calculate 12 - 11 + 10 - 9 + 8 - 7 + 6 - 5
6.
How many 2-digit even square numbers there are.
16, 36, 64
7.
The sum of the digits of 1 million times 1 million times 1 million times 1 million.
The first 1 digit is 1, the rest are 0.
8.
The number of even factors of 16.
2, 4, 8, 16.
9.
The area of the square whose perimeter is 4.
The side length would be 1.
10.
The base of a right-angle triangle with height 4 and hypotenuse 5.
Pythagoras' theorem.
11.
The number of fractions between 2/3 and 4/5 that can be written as a/30 (not including 2/3 and 4/5, and a is a whole number.)
Converting you have: 2/3 = 20/30, 4/5 = 24/30. So a could be 21, 22, 23.
12.
The difference between 2 cubed and 2 squared.
2 cubed = 8, 2 squared = 4.
13.
How many prime numbers divide 60.
They are 2, 3, 5.
15.
Half of the reciprocal of a quarter subtracted from a half.
Half subtract a quarter = a quarter. Reciprocal of a quarter = 4.