Assuming 6 legs for each insect, 17 insects will have 102 legs.
But, there are 122 − 102 = 20 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 20 extra legs belong to 10 spiders.
Alternative Solution through Equations:
be the number of spiders and f
be the number of flies. Then,
= 17; and
On solving the above two equations, we get
+ 6 (17 − s
) = 122; or
= 122 − (6 × 17).
Food for thought:
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