I am thinking of a number if you add two to the number then double it, you get ten. what is the number?
2 answers:
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1. Since each child kicks the same number of times, it is not important whether he or she kicks 1 time, 2, 3 or more times. So let all of them kick 1 time.
2. assume we start with a girl. We can start with either of the 77 girls, then second is a boy which can be either of the 76, the third is a girl which can be either of the 76 remaining, then the forth is one of the 76 boys...
3. So starting with a girl we have
77*(77)*76*(76)*75*(75)....*2*(2)*1*(1)=77!*77!
4. OR we could have started with a boy, where we would get again 77!*77!
5. Answer: 77!*77!+77!*77!=2
2. assume we start with a girl. We can start with either of the 77 girls, then second is a boy which can be either of the 76, the third is a girl which can be either of the 76 remaining, then the forth is one of the 76 boys...
3. So starting with a girl we have
77*(77)*76*(76)*75*(75)....*2*(2)*1*(1)=77!*77!
4. OR we could have started with a boy, where we would get again 77!*77!
5. Answer: 77!*77!+77!*77!=2