Math Is Fun Forum

anyarules

Member

Registered: 2005-07-24

Posts: 29

logics teaser PLEASE

I seriously need this...

1.  Our grade held a pet day last week. We had dogs, cats, mice, some budgies and even a lizard. During maths, we counted the legs - 54. If there were 16 animals altogether, how many children brought in budgies?

2.  Some children from the local playgroup decorated their trikes and scooters the other day. If 7 children entered the parade and I counted 18 wheels, how many scooters were there?

3.  In a pet shop, I saw some lizards, a tortoise, some white rabbits, cats, dogs and birds. There were 5 birds. I counted 58 altogether. How many animals were there?

thanks

luca-deltodesco

Member

Registered: 2006-05-05

Posts: 1,470

Re: logics teaser PLEASE

#1

dogs cats mice lizards all have 4, so you can treat them as one thing, so what youre looking at is

4a + 2b = 54
a+b = 16, substituting b = 16-a we get
4a + 36 - 2a = 54, or 2a = 18, a = 9, b = 16-9 = 5

so the answer is 5 budgies

#2

same thing again

a+b = 7, a = 7-b
2a + 3b = 18, 14-2b + 3b = 18, b = 4, a = 7-b = 3

3 scooters

#3

if you mean 58, as in 58 legs. then the same thing again

lizards, turtles, rabbits, cats and dogs all have 4 legs, birds 2

4a + 10 = 58, 4a = 48, a = 12
a + 5 = c, c = 17

17 animals

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anyarules

Member

Registered: 2005-07-24

Posts: 29

Re: logics teaser PLEASE

OMG thank you sooo much