Bugs buster busts bugs

10% of 300 = 30 which means there are 30 spiders.

After removing the millipedes, $\frac{30}{x} = 0.2$ or 20% where $x$ is the total number of bugs (millipedes and spiders).

This rearranges to $\frac{30}{0.2} = x$ , which means $x = 150$ . Now we know that there are 150 spiders and millipedes together. $300 - 150 = 150$ which means that Bugs Buster removed 150 millipedes.

Sum of spiders and millipedes is $300$ Wich spiders is $10 \%$ of sum. So, total of spiders is $\frac{10}{100}\times 300=30$

To make spiders is 20% from sum, Such as x is millipedes that removed

$\frac{30}{300-x}\times 100\%=20\%$ $\frac{30}{300-x}\times 100=20$ $150=300-x$ So, $x=150$

10% are spiders. 10% of 300 is 30. Therefore,spiders are 30 and millipedes will be 300 -30 =270. According to second condition, 20 % .x= 30. x= 150. Therefore, the total no. must be equal to 150. Of which 30 are spiders, therefore, millipedes will be 120. So, we have to subtract 150 from 270 ,to get 120. Hence the answer is 150.

Let he have to remove $x$ millipedes.

Then, Current millipedes = $300 * \frac{90}{100}$ = $270$

Current spiders $300-270 = 30$

After removing, No. of spiders will be same and millipedes will be decreased . So, the total No. of bugs will be decreased .

And the equation is $\frac{270 - x}{300-x} = \frac{100-20}{100}$ [ $\frac{Total No. of millipedes}{Total No. of bugs}$ = $150$

300 total 30 aranhas=10% 300-150=150 insetos(-150 centopeias) 120 centopeias=80% 30 aranhas=20%

There are 10% spiders out of 300. So, there are 30 spiders. Now we have to find a condition such that (30/x) = 0.20. This implies, x = 150. So, 150 millipedes have to be removed.

Currently there are 30 spiders and 270 millipedes. We have to find x such that 30+(270-x)=150 , as 30 is 20% of 150, thus x= 150

There are $0.1\cdot 300=30$ spiders in the tank. Now, Bugs buster removes millipedes, and the number of spiders doesn't change. Therefore, the number of spiders in the 20% spider tank is also 30. Then, the total number of bugs in the new tank is $5\cdot 30=150$ . This means that $300-150=\boxed{150}$ bugs were removed.

300*10% = 30 spiders .
Simply put, if there is twice the ratio of spiders left, then there must be half as many bugs left in total. 300/2 = 150 total. There are still 30 spiders as none were taken away, and so the 150 that were taken away must be millipedes.

I only thought of this afterwards, so here is the way I originally solved it:

30s (for spiders) + (300-30)m (for millipedes) = 300.

(300 - 30)m = 270m

30s + 270m = 300

30s+(270-x)m = 300-x = 30/20%
30s+270-x = 300-x = 150 300-150 = x

x = 150

This is where x is equal to the number of millipedes that have been removed.

He starts with 300 bugs so 10% of that would be 30 spiders. If he wants 20% of the bugs left to be spiders, he should end up with 150 bugs in total. So he started with 270 millipedes, so all he has to do is remove 150 millipedes, which is our answer.

Spiders - (10% x 300 = 30) Millipedes - (300 - 30 = 270)

We need to find the total number of bugs, where 20% of the bugs will be spiders. Remember that the number of spiders do not changes, only the millipedes.

30/X x 100 = 20 0.2X = 30 X = 150

Total number of bugs = 150 Total number of millipedes = (150 - 30) = 120 So, the bugs buster need to remove 150 millipedes.