"I have just sprayed the kitchen with insecticide and killed a total of 15 flies and spiders. The dead flies and spiders had 100 legs altogether. How many spiders were there?"

I can't seem to figure it out..

My path of thought has so far has been:

s + f = 15
s = 15 - f
(this gives me the quantity of spiders)

Substituting in s = (15-f)
100 = (15-f) + f

And that is where I get stuck.

Question

"I have just sprayed the kitchen with insecticide and killed a total of 15 flies and spiders.  The dead flies and spiders had 100 legs altogether.  How many spiders were there?"

I can't seem to figure it out..

My path of thought has so far has been:

s + f = 15
s = 15 - f
(this gives me the quantity of spiders)

Substituting in s = (15-f)
100 = (15-f) + f

And that is where I get stuck.

shamil98 · Answer

Spiders have 8 legs right?
flies have two?..
I would say 10 spiders and 10 flies

jack1 · Answer

s = spiders
f = flies
spiders have 8 legs each
flies have 6 legs each
$$ \large s+f = 15  = equation~1 $$
$$ \large 8s+6f = 100  = equation~2 $$
solve using substitution

shamil98 · Answer

oh flies have 6 legs.
 LOL

jack1 · Answer

;)

jack1 · Answer

@sam1ck solve using simultaneous equations given in above post, any q's write below an I'll get back to u if ya need a hand dude

anonymous · Answer

Oh d'uh!  It felt like it was missing something, cheers bud

jack1 · Answer

nah sweet as dude hey