Below are some wonderful links to Khan Academy videos we watched on the LCM and GCF in class. These are great review for students who need to brush up on the skills they learned in Grade 4!
https://www.khanacademy.org/math/arithmetic/fractions/Equivalent_fractions/v/finding-common-denominators
https://www.khanacademy.org/math/pre-algebra/factors-multiples/greatest_common_divisor/v/greatest-common-divisor
https://www.khanacademy.org/math/arithmetic/fractions/Equivalent_fractions/v/finding-common-denominators
https://www.khanacademy.org/math/pre-algebra/factors-multiples/greatest_common_divisor/v/greatest-common-divisor