Assuming 6 legs for each insect, 12 insects will have 72 legs.
But, there are 78 − 72 = 6 extra legs.
It is important to note that spiders have 8 legs and flies have 6 legs. So, there are 2 extra legs per spider on the web.
Thus, the 6 extra legs belong to 3 spiders.
Alternative Solution through Equations:
be the number of spiders and f
be the number of flies. Then,
= 12; and
On solving the above two equations, we get
+ 6 (12 − s
) = 78; or
= 78 − (6 × 12).
Food for thought:
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