Ms. Hatcher teaches 20 third-graders and a number of fourth-graders that is twice the number of third-graders. Her co-teacher asked her to substitute for her fifth-grade class that has half as many students as the number of third-graders. How many students did Ms. Hatcher teach for the day?
Ms. Hatcher taught 20 x 2 = <<20*2=40>>40 fourth graders for the day.
She taught 20 / 2 = <<20/2=10>>10 fifth-graders as a substitute teacher for the day.
Therefore, she taught 20 + 40 + 10 = <<20+40+10=70>>70 students for the day.
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