机器 A 每分钟比机器 B 多打印 10 页。机器 C 的打印速度是机器 A 的一半。这三台机器在 3 分钟内共打印了 270 页。按此速率，机器 C 在 1 分钟内打印多少页？ 答：___

1. Find the total number of pages printed by the three machines in 1 minute.

Total pages in 1 minute = $270 \div 3 = 90$

2. Set up an algebraic expression for the printing rate of each machine.

Let Machine A print $2u$ pages per minute.
Machine C prints half as fast as A, so Machine C prints $u$ pages per minute.
Machine A prints 10 pages more than B, so Machine B prints $2u - 10$ pages per minute.

3. Form an equation using the total printing rate and solve for $u$.

Total rate = $2u + (2u - 10) + u = 90$
$5u - 10 = 90$
$5u = 100$
$u = 20$

4. Calculate the number of pages Machine C prints in 1 minute.

Machine C prints $u$ pages per minute.
$u = 20$