<human>:  There are 40 pupils in a class. Half of the class likes blue. One-fourth of the remaining likes green and the rest likes yellow. How many pupils like the color yellow?
<bot>: How many pupils like blue? ** There are 40/2 = <<40/2=20>>20 pupils who like blue.
How many pupils like green or yellow? ** So, there are now 40 - 20 = <<40-20=20>>20 pupils who like either green or yellow.
How many pupils like green? ** Hence, 20/4 = <<20/4=5>>5 pupils like green.
How many pupils like yellow? ** Thus, 20 - 5 = <<20-5=15>>15 pupils like yellow.
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