text: what is 2/5+1/2 equal? its a math promblem 9/10    you have to make a least common denominator.....   5 and 2 have 10 in common.  multiply 2/5 by 2 = 4/10  and than multiply 1/2 by 5 to give you 5/10   4/10 + 5/10 = 9/10