Multiplication by two quiz for students. This is a basic skill. Multiplying a number by two implies adding that number to itself. Hence in this example, 5 x 2 = 5 + 5; the same rule applies for any other number being multiplied by two. The outcome of such numbers is a multiply of two and is an even number. Teach kids in 2nd, 3rd, 4th and 5th grades to multiply by two.