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An entomologist always keeps a few ‘pets’ at home and currently has some spiders, beatles, and an assortment of apodous larvae. She has less larvae than spiders and beatles combined. Altogether in the collection there are seventeen heads and fifty-eight legs. How many spiders does the entomologist keep?

pengangiie  May 6, 2015

Best Answer 

 #1
avatar+26322 
+10

Spider:   1 head  8 legs

Beetle:   1 head  6 legs

Larva:    1 head  0 legs (?)

 

S + B + L = 17  ...(1)

S + B > L          ...(2)

8S + 6B = 58    ...(3)

 

Solving (1) and (3) for S and B we get

S = 3L - 22   ...(4)

B = 39 - 4L   ...(5)

 

From (4) we see that L must be greater than 7 or S will be negative.

Try L = 8

S = 2,   B = 7    and S + B = 9 which is greater than L consistent with (2)

 

Try L = 9

S = 5, B = 3   and S + B = 8 which is less than L so not consistent with (2)

 

L must be less than 10 or B will be negative

 

Therefore there must be 2 spiders (and 7 beetles and 8 larvae).

.

Alan  May 6, 2015
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3+0 Answers

 #1
avatar+26322 
+10
Best Answer

Spider:   1 head  8 legs

Beetle:   1 head  6 legs

Larva:    1 head  0 legs (?)

 

S + B + L = 17  ...(1)

S + B > L          ...(2)

8S + 6B = 58    ...(3)

 

Solving (1) and (3) for S and B we get

S = 3L - 22   ...(4)

B = 39 - 4L   ...(5)

 

From (4) we see that L must be greater than 7 or S will be negative.

Try L = 8

S = 2,   B = 7    and S + B = 9 which is greater than L consistent with (2)

 

Try L = 9

S = 5, B = 3   and S + B = 8 which is less than L so not consistent with (2)

 

L must be less than 10 or B will be negative

 

Therefore there must be 2 spiders (and 7 beetles and 8 larvae).

.

Alan  May 6, 2015
 #2
avatar+90988 
+5

You have repeated this question without stating that it is a repeat question.

 

PLEASE DO NOT DO THIS!!

Alan and i have both answered you and as a result other question will not be answered.

There is not time to answer all!

You are invited to repost - that is fine BUT  please follow the intstuctions that i have laid out here.

http://web2.0calc.com/questions/instructions-on-reposting_1

 

My solution is here:

http://web2.0calc.com/questions/question-3

Melody  May 6, 2015
 #3
avatar+78577 
0

Vey nice, Melody and Alan.....

 

  

CPhill  May 6, 2015

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