   SEARCH HOME Math Central Quandaries & Queries  Question from chasity, a parent: a teacher wishes to schedule a quiz during part of a two-hour class. the equation 1+e=120 can be used to find the available lecture time "1" given that "e" minutes are planned for the quiz. determine the ordered pairs that satisfy the equation if the domain is {20,30,45,60} Hi Chastity,

I am going to use L and E as the two variables since lower case L looks too much like a one.

The time available for the class is 2 hours or 120 minutes. E is the number of minutes used for the quiz and L is the number of minutes used for the lecture. Thus L + E = 120. One way to solve this problem is to use a table.

E L L + E
20 100 120
30 90 120
... ... ...

The ordered pairs so far are (20, 100) and (30, 90).

Complete the table by adding two more rows and then complete the list of ordered pairs.

I hope this helps,

Penny     Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences.