Question

Out of $20$ creepy-crawly creatures in a room, $80\%$ are flies and $20\%$ are spiders. If $S\%$ of the total legs belong to spiders, what is $S$?

Answer 1

25

Explanation:

There are (0.8) ∙ 20 = 16 flies, with a total of 16 ∙ 6 = 96 legs.

There are (0.2) ∙ 20 = 4 spiders, with a total of 4 ∙ 8 = 32 legs.

Therefore, the total number of legs belonging to all the flies and spiders is 96 + 32 = 128. The fraction of these which belong to spiders is 32\128, which can be simplified to 1/4. As a percentage, this is 25%, so S = 25.

Answer 2

Answer: 25

Explanation:

Since, Total creepy-crawly creatures = 20

Out of which 80% are flies and 20% are spiders,

Thus, the total flies = 80% of 20 = 16

And, The total spiders = 20% of 20 = 4

Also, we know that the number of legs of a spider = 8,

⇒ Total legs belong to spiders out of 20 creepy-crawly creatures = 4×8 = 32

Again, the number of legs of a fly = 6

Thus, the total legs belong to flies out of 20 creepy-crawly creatures = 6×16 = 96

Hence, Total legs = 32 + 96 = 128

`\text{ The percentage of legs that belongs to spider} = \frac{ \text{ Number of legs of 8 spiders}}{\text{ Total legs}}* 100`

`= (32)/(128) * 100`

`= (3200)/(28)`

`= 25\%`