Problem solving

Answer the following. Justify your solutions.

Cafeteria survey

A cafeteria survey shows that 125 students like steak, 60 like shrimp, and 40 students like both steak and shrimp. Assuming that all of the students surveyed liked at least one of the options, how many students were surveyed?


Cooking survey

A student was asked to interview at least 140 people about their cooking habits. She handed in the following results. Did she interview at least 140 people?


 


Near-sighted lawyers

In a group of 37 people, 18 are neither near-sighted nor lawyers. Ten are near-sighted and 13 are lawyers. How many lawyers in the group are near-sighted?


Thingamajigs

Every doodad is a doohickey. Half of all thingamajigs are doohickeys. Half of all doohickeys are doodads. There are 30 thingamajigs and 20 doodads. No thingamajig is a doodad. How many doohickeys are neither doodads nor thingamajigs?


For more explanation and practice, see http://www.purplemath.com/modules/venndiag4.htm