【Question 10】
Red pens cost 5 yuan each, blue pens cost 7 yuan each, spending 102 yuan in total for 16 pens, bought $\qquad$ blue pens.
【Analysis and Solution】
Chicken and rabbit in the same cage.
(Method One)
Assume 102 pens are all red pens, then it would cost $5 \times 16=80$ yuan; which is $102-80=22$ yuan less than the actual amount;
One red pen costs $7-5=2$ yuan less than one blue pen;
The number of blue pens bought is $22 \div 2=11$.
(Method Two)
Assume 102 pens are all blue pens, then it would cost $7 \times 16=112$ yuan; which is $112-102=10$ yuan more than the actual amount;
One blue pen costs $7-5=2$ yuan more than one red pen;
The number of red pens bought is $10 \div 2=5$;
The number of blue pens bought is $16-5=11$.