First figure out how many total calories come from the carrots by multiplying the calories per carrot by the number of carrots: 20 calories/carrot * 5 carrots = <<20*5=100>>100 calories
Then subtract the calories the kids have already eaten from the goal number of calories to find out how many more total calories they should eat: 750 calories - 400 calories - 100 calories = <<750-400-100=250>>250 calories
Then divide the total number of calories by the calories per cookie to find the number of cookies each kid gets: 250 calories / 50 calories/cookie = <<250/50=5>>5 cookies
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