Bugs buster loves collecting bugs in his tank. He has 300 spiders and millipedes in his tank, of which 10% are spiders. How many millipedes must he remove, such that 20% of the bugs that are left will be spiders?
+23246 There are 300 spiders and millipedes, of which 10% are spiders: 0.10 · 300 = 30.
He has 30 spiders and 270 millipedes.
He wants a group of millipedes and spiders to contain 30 spiders and these 30 spiders
are 20% of the group.
Let x be the total number of millipedes and spiders: 0.20 · x = 30
Dividing both sides by 0.20: x = 30 / 0.20 = 150.
He'll end with 30 spiders and 120 millipedes.
He'll need to remove 270 - 120 = 150 millipedes.
