## kmeds16 3 years ago In a family, each boy has as many sisters as brothers, but each sister has only half as many sisters as brothers. How many children are there in the family?

1. goformit100

ok

2. kmeds16

@Decart show me the solution please :)

3. kmeds16

Ah ok I got it by fingers. But is there any mathematecal equation to solve this kind of problem? Its like a riddle.

4. Decart

boys = x girls = y

5. campbell_st

there are 7 children, 4 boys and 3 girls...

6. kmeds16

@campbell_st can you show me your solution?

7. campbell_st

plenty of options...

8. cwrw238

i find this quite tricky..

9. Decart

two equations two unknowns

10. campbell_st

if you rewrite Decarts equations you have y = -1 and 0.5y - x = 1

11. kmeds16

oh wait. im still trying to figure it out. its tricky :/

12. campbell_st

for me it was trial and error knowing that there needed to be an odd number of children I knew 3 doesn't work, 5 works for the boy having equal sisters and brothers but doesn't work for the girl, so try 7 works

13. cwrw238

- thats probably the best way i've got a headache trying to create the equations

14. Decart

but we can get them

15. cwrw238

maybe i need another coffee - lol

16. kmeds16

@cwrw238 haha, my brother too. until he left me here alone :/

17. Decart

brother = x+y sister=x+.5y

18. Decart

.5y when we took one away

19. Decart

sister = 2x+y

20. Decart

brother is actually x+1

21. Decart

x+1brother has x-1+y x-1 being himself

22. cwrw238

1 + 2x = x + y where x = girls, y = boys is one equation

23. Decart

x+1+y=y-1+2x

24. cwrw238

that gives x + 1 = 1 + 2x giving x=0

25. kmeds16

i formulated an equation XD x - 1 = y y - 1 = x/2

26. cwrw238

x - 1 = 0.5y is another so u have 1 + 2x = x + y x -1 = 0.5y is that right??

27. kmeds16

@cwrw238 i'll try to solve yours & you try mine :)

28. cwrw238

yes that gives x = 3 y=4

29. cwrw238

oh ok

30. Decart

awesome

31. cwrw238

x - 1 = y y - 1 = 0.5x add x - 2 = 0.5x x = 4 y = 4-1 = 3

32. cwrw238

in your equation x = boys , y = girls right? yours come out right too

33. kmeds16

ya and yours is x = girls and y = boys,right?

34. cwrw238

yea well done

35. kmeds16

thank you @cwrw238 :)