Solving Equations using Cross Multiplication #equations #algebra #math #mathematics #mathtutor #mathtutorial #mathskills #mathtricks #mathchallenge #mathmadeeasy #mathisfun | Unang Math

12 year old Dawa is demonstrating to the class how the Moroccans, 500 years ago, could multiply and square their teen numbers, like 12x12 or 13x13 or 14x14 etc merely by curling some fingers. eg: take 13x13. How much is 13 more than the Base of 10. It is 3, so on your left hand curl 3 fingers and on the right hand curl 3 fingers again. Start with giving yourself the amount of 100. Add to this number of fingers curled, which 3 3 or 6 and multiply this by 10. So we now have 100 60 and add to this