<human>:  The pirates plan to explore 4 islands. Two islands require walking 20 miles per day while the other two islands require 25 miles per day. How many miles will they have to walk if it takes 1.5 days to explore each island?
<bot>: How many days will it take to explore 2 islands? ** It will take 1.5 days x 2 = <<1.5*2=3>>3 days to explore 2 islands.
How many miles will the pirates walk to explore two islands? ** So, the pirates will walk 20 miles x 3 days = <<20*3=60>>60 miles to explore two islands.
How many miles will the pirates walk to explore the other two islands? ** The other 2 islands will be explored by walking 25 miles x 3 days = <<25*3=75>>75 miles.
How many miles will the pirates walk to explore the 4 islands? ** Thus, the pirates will need to walk 60 + 75 = <<60+75=135>>135 miles to explore the 4 islands.
#### 135