<human>:  Martin is casting three bells for the church's belfry. The first bell takes 50 pounds of bronze, the second bell is twice the size of the first bell, and the third bell is four times the size of the second bell. How much bronze does he need total?
<bot>: How much does the second bell weigh? ** First find the size of the second bell: 50 pounds * 2 = <<50*2=100>>100 pounds
How much does the third bell weigh? ** Then find the size of the third bell: 100 pounds * 4 = <<100*4=400>>400 pounds
How much bronze does Martin need total? ** Then add the amount of bronze used for each bell to find the total: 100 pounds + 400 pounds + 50 pounds = <<100+400+50=550>>550 pounds
#### 550