Final answer:
A total of 13/20 of the pizza was eaten after Jack ate 1/4 and Mario ate 2/5. The fractions were converted to a common denominator of 20 and then added together.
Step-by-step explanation:
The question asks how much of a pizza was eaten if Jack ate 1/4 of it and Mario ate 2/5. To find the total fraction of the pizza that was eaten, we simply add these two fractions together. However, before we can do that, we need to have a common denominator. The smallest common denominator for 4 and 5 is 20.
Now, we convert each fraction to have the denominator 20. For Jack's portion, we multiply the numerator and the denominator by 5, which gives us 5/20. For Mario's portion, we multiply the numerator and the denominator by 4, which gives us 8/20. When we add those two fractions together, we get (5/20 + 8/20) which equals to 13/20 of the pizza eaten in total.