First print out the number of sheets you need for your classes, they are all different so that helps keep the students from getting the same ones plus all their answers will be different. Then print the "calling questions" for you.
Remind the students they must write only in INK and there must not be any scratch-out, changes, or their game sheet will not count. If they do not know an answer, the letter will be used later, again and again for different items.
Spelling should be correct but if you can read their answer, accept if you choose. When they get five in a row, up-down, side to side, diagonally, and you have quickly checked their answers, award the number of points/extra credit you have chosen to award before the game starts. Then you can keep playing until time runs out. I always awarded points in descending amounts until class was over.
There are 29 game boards and three question sheets.
This bingo game works very easy due to the fact that students make up their own answers and it makes it easy for any student because even if they don't know one answer, the letter will come up again with a new/different topic. I have used this over and over for my own students as a review, time-killer, end of six/nine weeks, before a holiday, visitors anything that I want to.
Have fun with it and email me and tell me how your students did. I would love to hear from you at firstname.lastname@example.org. Thanks.