What's up with that

In elementary school I always did like multiplying, dividing , a+b=c, and exponents also square rooting. What i would like to learn is like how to do multiple by like 20,30,40,50,60,70,80' and 90. And I like to do in class are like 5 minute math quizzes to help us get our brains working a little more. How I like to learn from like some videos and playing on the iPads and maybe small sheets. What would help me understand something's would be like try to explain it in simples way.