Ren can eat a pizza in 3 minutes and Isaac can eat a pizza in four minutes. How long will it take them to eat the pizza together?

Ren and Isaac will eat the pizza in a 7 minutes

1.71 min per pizza

Step-by-step explanation:

Ren's rate:

3 min per pizza (take inverse to get pizza per min)

= 1/3 pizza per min

Issac's rate:

4 min per pizza (take inverse to get pizza per min)

= 1/4 pizza per min

Combined rate = Ren's rate + Issac's rate

= 1/3 + 1/4

= 4/12 + 3/12

= 7/12 pizza per min (take inverse to get min per pizza)

= 1 / (7/12) min per pizza

= 12/7 min per pizza

= 1.71 min per pizza