# Free Practice 6.RP.A.3 – 9003201

Bob has to bring $4$ dozens of pens to school. Among $10$ pens he already has, $30\%$ of them are blue pens and the rest of them are black pens. Bob wanted to havehalf of black pens and half of blue pens out of total $4$ dozens. How many blue pens does he have to buy?
A. $21$
B. $38$
C. $17$
D. $45$
E. $3$