IR increases by a multiple?

IN CFAI reading 32 (Equity portf mgmt), EOC 11 solution explains that one combination of managers that generate an IR of 1.45 is better than the other that generates an IR of 0.67. however, they also mention that IR increases from 0.67 to 1.45 which is an increase by a factor of 2.17. how did they get 2.17???