If Katherine has 4 apples and 3 times as many pears in her fridge, how many bananas does she have if she has a total of 21 pieces of fruit?
Katherine has a total of 3 * 4 apples = <<3*4=12>>12 pears
She therefore had 4 apples + 12 pears = <<4+12=16>>16 apples and pears
We know she has 21 total pieces of fruit, so this means she must have 21 total - 16 = <<21-16=5>>5 bananas
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