A teacher has 21 red pens. If the ratio of red pens to blue pens she owned was 3:1, how many pens did she have total? It’s one of the word problems sixth-graders at Vera C. O’Leary Middle School were ...

Add Yahoo as a preferred source to see more of our stories on Google. Fifteen years after the calamitous rollout of the Common Core math standards, the once-derided strategy has proven its staying ...