3. A copy machine, working at a constant rate, makes 35 copies per minute. A second copy machine, working at a constant rate, makes 55 copies per minute. Working together at their respective rates, how many copies do the two machines make in half an hour?

Ans

Both copy machines will make (35*30) + (55*30) = 2700 copies in half hour

Explanation:

1st machine is making 35 copies per minute. In half hour there are 30 minutes so we multiply 35 with 30 to get 1050 for 1st machine.

For the 2nd machine it will be 55 copies per minute, and we multiply with 30 minutes to get 1650.

Adding the two will give us 2700 copies in half hour